Good question, but for musterion's sake, maybe he would have seen your question if you had put a ? question mark at the middle of your first sentence instead of a , comma. Ie, Could you please expand on this? I'm not sure exactly what you mean.
As your question points out. Flesh has a variety of nuances that must be recognized in order to rightly divide his passages and your passage.
Surely in the case of Philippians 1:21, flesh is a reference to Paul's physical body as in, body and soul and spirit, from I Thessalonians 5:23, " And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ." Surely, without a body and soul, we could not read or hear and believe God's word from scripture. We need our body and soul in order to read, via the five senses flesh/body - our eyes and ears, God's written word. Likewise we need our brains, which God provided in order to do that much, let alone process into our hearts and minds what God is communicating to us via His word.
In Musterion's passage, it is a reference to the carnal desires of the flesh and to information acquired by the five senses, ie, facts, ie, temporary, short lived knowledge, wisdoom and understanding, as opposed to
to the knowledge and wisdom and understanding that comes from God via His word, ie, scriptures, and the knowledge and wisdom and understanding that comes from believing God's word and putting to practice.