Have you verified the bitcoin supply yourself?
They're both math. One is addition, the other is a little more involved. But if the math is proven correct they're both equally verified.
Discussion
This one I do check. I understand your POV, but it is easily check able both the easy way (gettxoutsetinfo, getblockchaininfo) or writing a small program to calculate “manually” based on the reward logic
You can do the same thing with Monero, it's just verifying the range proof math and coinbase transactions.