And that other was Apollos of Alexandria, the author of 'Hebrews'.Perhaps Paul did not directly study Philo, he was building on teachings that were derived from Philo by others?
'Hebrews' is closer to Philo concepts than Paul was.
Some quotes from Philo's works:
a) "Now the image of God is the Word, by which all the world was made" (The special Laws I, ch. XVI)
b) "... the second deity, who is the Word of the supreme Being" (Questions and answers on Genesis II)
c) "For the Father of the universe has caused him to spring up as the eldest Son, whom, in another passage, he calls the firstborn. And he who is thus born, imitating the ways of his father ..." (On the confusion of tongues, ch. XIV)
d) "And even if there be not as yet one who is worthy to be called a son of God, nevertheless let him labor earnestly to be adorned according to his first-born Word, the eldest of his angel, as the great archangel of many names; for he is called the authority and the name of God and the Word, and man according to God's image ..." (On the confusion of tongues, ch. XXVIII)
e) "And this same Word is continually a suppliant to the immortal God on behalf of the mortal race which is exposed to affliction and misery; and is also the ambassador, sent by the Ruler of all, to the subject race. And the Word rejoices in the gift ..." (Who is the heir of divine things, ch. XLII)
f) "the most ancient Word of the living God ... he will never take the mitre off from his head, he will never lay aside the kingly diadem, the symbol of an authority which is not absolute, but only that of a viceroy, but which is nevertheless an object of admiration." (On flight and finding, ch. XX)
g) "the man [the high priest] who was consecrated to the Father of the world, should have as a paraclete [intercessor], his Son, the being most perfect in all virtue, to procure forgiveness of sins, and a supply of unlimited blessings..." (On the life of Moses II, ch. XXVI).
h) "Who then is the chief butler of God? The priest who offers libations to him, the truly great high priest, who, having received a draught of everlasting graces, offers himself in return, pouring in an entire libation full of unmixed wine" (On dreams II, ch. XXVII)
i) "For there are, as it seems, two temples belonging to God; one being this world [heaven], in which the high priest is the divine word, his own firstborn son."(On Dreams I, ch. XXXVII)
j) "For we say the high priest is not a man, but is the Word of God ..." (On flight and finding, ch. XX)
k) "Jesus means "the salvation of the Lord", being the name of the most excellent possible character" (On the Change of Names, ch. XXI) See Philippians 2:9 and Hebrews 1:4
Apollos attributed these concepts of Philo to Jesus. And what I outlined suggests a human Jesus.
And concepts and other items in 'Hebrews' made their way in Paul's epistles, such as (from 'Hebrews'):
(pre-existence (explained) (1:1-3a,5-10,2:5-8), Sacrifice (explained) (1:3,5:8-9,7:27,9:11-15,10:1-14), (Jesus') blood (9:12,10:19,29), co-Creator of the universe (explained) (1:2,10), Moses' followers dying in the wilderness (3:16-17), home in heaven for Christians (12:22-23), atonement for sins (explained) (1:3,2:17,10:12), "Son of God" (explained) (1:5,8-9), Christians as seed and heirs of Abraham through the "promise" (2:16,6:13-17), the heavenly Jerusalem (12:22-23), Jesus offering himself for sacrifice for atonement of sins (explained) (7:27b,10:12), "at the right hand of God" (explained) (1:3,13,8:1,10:12,12:2), "firstborn" (explained) (1:6,12:23), Jesus interceding with God in behalf of Christians (explained) (7:25))