zunionstore/zinterstore works on sets, why doesn't the command doc mention it?

[sgon00]

In https://redis.io/commands/zunionstore and https://redis.io/commands/zinterstore, it doesn't mention a single word about I can use set as one of the key too. Why is that? Is this not recommended?

> ZADD zset1 1 "one"
> SADD sset "two"
> ZUNIONSTORE out 2 zset1 sset
> ZRANGE out 0 -1 WITHSCORES
one
1
two
1

Thanks a lot.

PS: I just learnt I can do this today. If it's OK to be used like this, I need to redesign my entire redis db... Because at the first time I read redis.io, I don't find anywhere mention this. I am wondering If this feature is not recommended (deprecated) and will be removed in the future or not. Cheers.