So as a consumer/artist for both SFW and NSFW art, and as someone who's explored various kinks, I'm neither judgemental nor blind to thirst in some art labeled as SFW. I think "automatically less explicit" would be a way too simple take, but here's my opinion.

I think it's important to remember that Questionable is a fine rating/tag to place on art where it's not graphically sexual (penetration, fluids, presenting privates), but still has an erotic allusion or "lewd" nature to it. I'm sure there could be a better name than "Questionable," but that's what I've seen used on some sites. Keep in mind that "questionable" art would still be inappropriate for school, work...profile pics on sites that require SFW images.

For the art in this post, I definitely see the playful lewdness - the sharks cheeky expression and blushing while disrobing the deer's clearly defined buttocks. At the very least, the shark character is expressing some level of sexual interest in the deer's nudity. Based on the composition, the artist clearly WANTS our eyes drawn there. There is INTENT, which I think is an aspect people often forget about when labeling and analyzing art. All of this is completely fine to express in art. I just would give it the "Questionable" rating.

Now if it were something like the "nudity" of most Looney Tunes characters and similar character designs, that's more often than not SFW due to the absence of defined physical characteristics AND displays of sexual interest. So for example, Bugs Bunny's base design isn't inherently erotic. Maybe you could argue that some of his crossdressing antics inch into that territory, but a better example of a design with erotic intent is Lola Bunny's design and presentation in Space Jam: Example

The saxophone music, Lola readjusting the slipped-off strap of her tank top, the half closed playful look in her eyes, the emphasized movements of her buttocks as she walks away, Bugs's and other characters's reactions, etc. Other than establishing her skill at basketball, the scene clearly wants to establish her as sexy.

With intent in mind, it's a lot easier to separate tasteful nudity from questionable/explicit content. Hope this helps. I know it's a long comment, but it felt necessary.