"Members of this forum" people, though to be fair, most commonly it’s phrased as a question “is so-n-so this other entity” and most commonly the consensus is “nope”.
If you hang around or try the search you’ll see them, it’s a common ask.
It’s always from newbies who are armchair mages, getting way stuck in their heads who have not evoked them separately to feel the energy signature: all beings including humans have a unique energy signature that cannot be faked. It can be imitated and then it depends on your skill to tell. That’s what impostors are all about.
When you do that it’s as obvious as seeing two people in a room who is the same and who isn’t, though it’s harder to sense when you have an egregoric overlay or an incarnation and when you don’t: that can feel like a new being and it kinda is and kinda isn’t. Like, you in your car and you walking aren’t the same but yet it’s still you underneath. Likewise, you will also be able to feel when they are the same. When you can so that you can also feel when you have an impostor, that that’s a vital skill for people who evoke.
I think though, this is a different question than, “do these two guys share an archetype”. The OP isn’t about archetypes or aspects, it’s asking why people try to conflate named entities. LOTs of entities share related attributes, as do lots of people.
E.g., I’m Aquarian, so is Belial, that doesn’t mean I AM Belial, we just both agree on the values of freedom and independence.
Here is an example for Lilith, trying to conflate Lilith, a Jewish figure “female evil spirit, in medieval Hebrew folklore the first wife of Adam, from Hebrew Lilith, from Akkadian Lilitu, which is connected by folk etymology with Hebrew laylah "night.” - etymology online" with everybody from Isis to Freja to Chinese deities, who do not have matching aspects, it’s all based a mix of documentation and hearsay and… really just wishful thinking.
I have no idea why, I think it’s diminishing and reductionist not helpful. And again, doesn’t bear out in ritual, which is the material point for a practicing mage trying to get results.