Such a practice is common and the government of El Salvador must have thought about it. Of course some real data verification will be done on wallets issued by Elsalvador, it won't be that easy to earn $30 with multiple wallet accounts. Verification of the original data is still required.
Not being forced to use an official wallet, of course, has a reason so that cryptocurrency users in El Salvador are saturated and have other options for using different applications. But what makes it interesting and must be used is the $30 reward for those who use and verify the data in the chivo wallet application.
If I am not wrong, when Coinbase was first launched in 2013, they had a similar airdrop. I don't remember the value exactly, but it was either
BTC0.01 or
BTC0.001 (back then the exchange rates were low). A majority of the users just created a new account, and then closed it as soon as they received the airdrop. But a small minority didn't dumped their coins immediately and started accumulating BTC. The latter group benefitted from the bull run of 2013, when the prices jumped by as much as 200x. The airdrop from Chivo sounds similar. KYC is needed, in order to stop scammers from creating dozens of accounts and claiming the airdrop with unfair means.