html minifer mostly just remove the whitespaces. Compression (gzip or brotli) preserves the source, i.e. decompressed file is exactly the same as the original's; whereas minifier alters the source.
Minifying HTML just makes your page source slightly harder to look at. Whitespace would be squashed into almost nothing with in-transit compression.
Probably something nobody ever needs to think of, but as a web dev it’s an argument I’ve had more than once!