I think it's safe to assume that when the PPS does come, it'll have the PPS tag to avoid confusion
I recall a staff member saying once that a PPS pet that grows in any way prior to becoming a PPS will have the tag. PPS pets that do not have the tag are generally ones that you receive already in their PPS state (such as from an event box). Even then, some of those might have the PPS tag, but I recall a staff member saying that artists can elect to leave it off in those instances (if I'm remembering correctly)
I can see how the double pet thing in Lilan's, or the size of Sketchi's might confuse people into thinking that they are the PPS pet in some way, but I think it's safe to say that they would have the PPS tag if that were the case, and would likely not feature any linework from the adult dog lines
Keep in mind that last year's staff litter had a pet like this that was not the PPS, as it technically "grew" to a distinct third stage
This was the actual PPS of the litter, with the PPS tag