Yes, you're getting the exact same chassis with the exact same coating/finish that was present on the M2 Airs. Also the same colors.
Wifi speeds being up to 2x faster, dual external display support, AV1 video-encoding, and the SoC being up to 1.3x faster than M2 are the only upgrades for MacBooks M3 Air over MacBooks M2 Air.
Everything else is exactly the same as M2.
Well, there also seems to be some vague-ish upgrades in terms of built-in microphones and speakers. And maybe a downgrade of sorts?:
View attachment 2355394
Maybe Apple wants the already upgraded speakers on the 15" Air to seem even more worth it and push a bigger purchase? Idk. But I'm sure reviews and tear-downs will clear this up.