I don't know why this question never occurred to me before.
"How can a block reward be a number of XMR other than a whole integer amount?"
Obviously, we all know that unlike the traditional stock market, which only trades in integer numbers of shares, almost all cryptoassets can be broken down into smaller portions. Bitcoin has the Satoshi, ETH has the Gwei, Litecoin has the Litoshi, Monero has the Piconero, etc. So there is no technical barrier from a transaction which moves less than exactly one XMR, or any amount including decimal places.
But when a block is mined, new XMR is "created." I don't believe the term is "forged," because I think that relates to DPOS. Some chains use the word "minted." Anyway, regardless of the terminology, most other blockchains that I'm aware of use whole integer multiples of the coin as a block reward (although BTC is down to 6.25).
So when a block is mined, let's say that the current Monero reward is around 0.8 XMR. How exactly does that amount get generated? Where does it come from? Due to tail emission, the coin supply is technically infinite (although quite constrained in a practical sense). There can't be a single private key with an infinite supply that releases 0.8 XMR from the vault. Does exactly one XMR get created and the remainder (0.2 XMR) get sent to a burn address to net out 0.8 XMR?
I'm embarrassed to admit that I don't know the answer to such a fundamental question. I feel that I should slink away and read the source code of the BTC protocol, to learn more.