It's only for 2-3 meals but you never know how they could use your KYC..
Just as a reminder to be be careful, but if you are sure this project is safe, you can surely do that.
Well, while I'd fully agree not providing your personal data to every shitty airdrop, blockchain.com should be quite trustworthy and I doubt they're selling your personal data.
I also participated in the airdrop and if I remember right it was about 25$ worth of XLM + a verified blockchain.com account. However it would be kind of interesting if they're deleting the data after verification or if they're storing it (should be possible to request a deletion as they seem to operate inside the EU).
Fortunately KYC should block most of this cheating-attempts (exactly that's the reason why so many (airdrops)/bountys require KYC... because of those cheating idiots)