Spirits are not deconfirms in any way whatsoever. If they are, that's 1200+ deconfirmed characters and it would be easier to tell who's going to be DLC by checking who isn't a spirit.
Well I mean, Konata Izumi is supposedly "loli" despite being 18, so maybe it's an appearance thing. So I guess they go by the definition that if a character looks visibly younger than 16 they're a loli, and Lip definitely looks like a very young girl. But whatever, "people drawing porn" is not a good reason to exclude a character.
She's been getting more and more support lately, but back in the Brawl and, to some extent, SSB4 days I know there were a tragic number of people who didn't want Lip in the game because she's a "loli" (she isn't) and they didn't want people to draw porn of her now.
All the fat/feeding/bara scaly porn of Bowser and K. Rool is far more degenerate and still not enough to exclude them so why should it be for Lip?