For Paul, the greek word translated “revelation” (apokalypsis, ἀποκάλυψις) automatically denotes a purely non-physical event.
• Richard Carrier: “The word for "revelation" is apokalypsis, the same word used for the title of the New Testament book of Revelations, and as there and elsewhere it means ‘manifestation’ in a spiritual sense—a vision. [Why I Don't Buy the Resurrection Story 6th ed. (2006)]
• Paul regularly uses ἀποκάλυψις to refer to an extra-mental event. 1
On the assumption that Paul experienced an extra-mental appearance of Jesus and wanted to communicate this, there is much clearer verbiage Paul could have used to communicate this physicality.1
But so what? Plausibly…
• That wasn't Paul's goal, and he had reason to use this revelatory verbiage.2
• Richard Carrier: “Paul has thus completely omitted any reference to conversations with a flesh-and-blood Jesus, as well as any witness or physical evidence of such a thing. That Christ is raised is known from scripture, which is known because Christ "revealed" it in a spiritual epiphany after his death. This fits perfectly a situation where his body remains buried, for then the only way it could be known that he had been raised (exalted and reembodied in heaven) would be through the spiritual revealing of hidden meaning in scripture.” [The Spiritual Body of Christ and the Legend of the Empty Tomb (Prometheus, 2005).]
• N. T. Wright: “[t]he rhetorical needs of Paul’s argument lead him naturally to stress the difference between the ‘revelation’ he received and the possibility that he had ‘received’ his gospel from ordinary human sources, some way down a chain of tradition, in such a manner that the Galatians could then appeal over his head to the original source. This is why he chooses the apokalypsis root to make the point: this was an ‘unveiling’ of the truth itself, indeed, of Jesus himself, not a secondary handing on. The word carries the overtones of the sudden uncovering of something previously concealed, in particular of something hidden in God’s sphere of reality (‘heaven’), something which would not normally be visible in the human sphere (‘earth’), but which could become so under special circumstances. Elsewhere in Paul this word-group has an eschatological force: something which one might expect to become manifest on the last day has been ‘revealed’ ahead of time. Since these are the particular emphases Paul wants to draw out here, we cannot deduce anything from this word about the exact type of experience (ordinary seeing, or ‘seeing’ in the heart).” [The Resurrection of the Son of God (Fortress, 2003), 379.]