Candle_Set.FBX file (you can find it in attached project) started to introduce warning in 2019.3 (uses Asset Pipeline v2).
There is no warning in 2019.3.0a3.
But there is warning in 2019.3.0a7 and a9.
So it could be a regression or improvement.

How we can reproduce it using the example you attached
1 Simply open attached project in 2019.3.0a7 or later build
(To reproduce this warning in already opened project - select Candle_Set.FBX file in Project view, click Right Mouse Button and select Reimport )

Actual results: 2 same warnings appear in Console:
"Identifier uniqueness violation: 'Name:Candle, Type:Mesh'. Multiple Objects with the same name/type are generated by this Importer. There is no guarantee that subsequent imports of this asset will properly re-link to these targets."

Expected results: not sure if this is a regression or improvement
----
Note: The warning was recently pulled down to the base importer (used to be only in the scripted importer) so it may start appearing in more asset types.
However it's not a regression, it's just the pipeline giving more info to the user in a situation that was just silently happening before already.