Very recently, someone got banned for badly tagging some pictures, and seeing how this kind of mistagging seems like anyone could be doing by mistake, I'd rather not take this route myself an actually ask for more clarification.
Anthro, from my own experience and from the wiki seems to basically mean anything that has a body similar to a human proportions wise, like the head being about 1/7 the height and so on. Semi-Anthro is a loose way to sort those characters that are right between anthro and feral, which is what I'd think of most of chibi/cute characters like Gatomon and for this case, Kero/Suppie.
If you think about it, these two fit right in the description of a semi-anthro since they're basically "walking ferals", and they have a simple looking body not remotely close to anthro looking, having arms/legs basically being long strips of cute fluff and the head taking 1/3 of the total height.
I noticed my Kero being tagged as anthro and corrected it to semi-anthro, then remembered that this guy got banned for mistagging things and quickly went full paranoid and looked at the other pictures of Kero, and saw that they were also being tagged as anthro, but after the quick look on the wikis, I'll think they and other characters like these two should be tagged semi-anthro instead.
The Anthro wiki should emphasize if similar proportions to humans are needed or not. The description is sort of vague on that, only saying they should be similar to humans. The examples given all have human proportions but without any clear mention, I can't know for sure if proportions actually matter or not
Updated by NotMeNotYou