if you have torches in your off-hand and a shovel in the other and you're making a grass path, commonly a torch may get placed instead.

Also, torches can be placed on red_sand

I noticed this on:
paper -1.16.2 r 174 +
EHM 3.14.1

I think the soft materials thing is a static list of materials. Is there a bukkit tag for sand? Just trying to think of ways to make this more easily maintainable.

How about adding config option "soft-blocks:"
Then you do not have to maintain.

That is an option.

It also can lead to different support requests, I.e. People who don't know about bukkit materials, try to fix with vanilla names, or simply not understanding why it no longer works/not aware of config.

If there's no good "built-in" way then it probably would be better to make it a config.