Verbose Mode during startup not working on Apple Silicon
In the past, verbose mode showed on the screen information that was logged by the kernel processes to traditional files. Also in the past, the logging system was overhauled to write these logs to a database first so they can be queried and some but not all of the logs end up in files.
Now, you can’t see the messages on screen and have to either know which files contain portions of the logged messages or query the database directly after the system has started (or indirectly if the system never completes startup).

Where to see kernel startup messages after boot?

Addressing the “what changed” with Apple Silicon is Apple completed the transition to all machines running under a T2 with a Secure Enclave and other architectural changes to the startup process. Some of these were present in Intel, but legacy behavior remained while Intel was executing the kernel code.
The old non-volatile ram commands don’t “work” on Apple Silicon.

Is there an equivalent to resetting NVRAM on an M1 mac?

Your diagnosis is correct - the store still sets values, but the system doesn’t take any action or read them at boot as far as I can tell.