The tag implication #43575 smelling -> sniffing has been rejected.

Reason: in fact, these are synonyms
if the author meant another meaning there are smelly/stinky

EDIT: The tag implication smelling -> sniffing (forum #328964) has been rejected by @gattonero2001.

If they're synonyms, shouldn't it be an alias?

Wiktionary said:
1. To sense a smell or smells.

• Smell the milk and tell me whether it's gone off.

2. To have a particular smell, whether good or bad.

• The roses smell lovely.

An alias to "sniffing" would be inconsistent with the second meaning of the verb, in cases like this one it's better to disambiguate the tag.

gattonero2001 said:
An alias to "sniffing" would be inconsistent with the second meaning of the verb, in cases like this one it's better to disambiguate the tag.

That applies to smell, not smelling, which is just a verb referring to the one performing the action. You can’t say “that is smelling bad,” the correct way to say that is simply “that smells bad.” So, I say +1 for aliasing. This sounds like it would be one of those disambiguations that’s going to cause more trouble than it’s worth: people using the word for its one grammatically valid meaning, not checking to see that it’s been aliased to a disambiguation, then filling the invalid tag with what easily could have been aliased to a valid tag instead. Glancing through the results for smelling, I don’t see anything that isn’t sniffing.

I would think it would more useful the other way around.

The tag implication smelling -> sniffing (forum #328964) has been rejected by @gattonero2001.