You know perfectly well that this is referring to a particular holiday (the horn-blowing one), and one cannot infer from this that all New Moon festivals are rest days.
Try again.
You are wrong, Sabbaths and all new moon days are shown as days when there was feasting and sacrifices done as the verses below show, not just the 1st of Tishri:
Numbers 28:11
'Then at the beginning of each of your months you shall present a burnt offering to the LORD: two bulls and one ram, seven male lambs one year old without defect;
Numbers 10:10
"Also in the day of your gladness and in your appointed feasts, and on the first days of your months, you shall blow the trumpets over your burnt offerings, and over the sacrifices of your peace offerings; and they shall be as a reminder of you before your God. I am the LORD your God."
Psalm 81:3
Blow the trumpet at the new moon, At the full moon, on our feast day.
Numbers 28:11-15
'Then at the beginning of each of your months you shall present a burnt offering to the LORD: two bulls and one ram, seven male lambs one year old without defect; and three-tenths of an ephah of fine flour mixed with oil for a grain offering, for each bull; and two-tenths of fine flour mixed with oil for a grain offering, for the one ram; and a tenth of an ephah of fine flour mixed with oil for a grain offering for each lamb, for a burnt offering of a soothing aroma, an offering by fire to the LORD.
1 Chronicles 23:30-31
They are to stand every morning to thank and to praise the LORD, and likewise at evening, and to offer all burnt offerings to the LORD, on the sabbaths, the new moons and the fixed festivals in the number set by the ordinance concerning them, continually before the LORD.
2 Chronicles 2:4
"Behold, I am about to build a house for the name of the LORD my God, dedicating it to Him, to burn fragrant incense before Him and to set out the showbread continually, and to offer burnt offerings morning and evening, on sabbaths and on new moons and on the appointed feasts of the LORD our God, this being required forever in Israel.
2 Chronicles 8:12-13
Then Solomon offered burnt offerings to the LORD on the altar of the LORD which he had built before the porch; and did so according to the daily rule, offering them up according to the commandment of Moses, for the sabbaths, the new moons and the three annual feasts--the Feast of Unleavened Bread, the Feast of Weeks and the Feast of Booths.
2 Chronicles 31:3
He also appointed the king's portion of his goods for the burnt offerings, namely, for the morning and evening burnt offerings, and the burnt offerings for the sabbaths and for the new moons and for the fixed festivals, as it is written in the law of the LORD.
Nehemiah 10:32-33
We also placed ourselves under obligation to contribute yearly one third of a shekel for the service of the house of our God: for the showbread, for the continual grain offering, for the continual burnt offering, the sabbaths, the new moon, for the appointed times, for the holy things and for the sin offerings to make atonement for Israel, and all the work of the house of our God.
Ezekiel 45:17
"It shall be the prince's part to provide the burnt offerings, the grain offerings and the drink offerings, at the feasts, on the new moons and on the sabbaths, at all the appointed feasts of the house of Israel; he shall provide the sin offering, the grain offering, the burnt offering and the peace offerings, to make atonement for the house of Israel."
Ezekiel 46:1
'Thus says the Lord GOD, "The gate of the inner court facing east shall be shut the six working days; but it shall be opened on the sabbath day and opened on the day of the new moon.
1 Samuel 20:5
So David said to Jonathan, "Behold, tomorrow is the new moon, and I ought to sit down to eat with the king But let me go, that I may hide myself in the field until the third evening.
2 Kings 4:23
He said, "Why will you go to him today? It is neither new moon nor sabbath." And she said, "It will be well."
Amos 8:5
saying, "When will the new moon be over, So that we may sell grain, And the sabbath, that we may open the wheat market, To make the bushel smaller and the shekel bigger, And to cheat with dishonest scales,
Isaiah 1:13-14
"Bring your worthless offerings no longer, Incense is an abomination to Me New moon and sabbath, the calling of assemblies-- I cannot endure iniquity and the solemn assembly. "I hate your new moon festivals and your appointed feasts, They have become a burden to Me; I am weary of bearing them.
Hosea 2:11
"I will also put an end to all her gaiety, Her feasts, her new moons, her sabbaths And all her festal assemblies.