That is a very good possibility. The magazines that come with the Competitor could also be made with the longer baseplate so that it can be easily inserted and still extend past the bottom edge of the magwell, if that is installed.
That's one small criticism I have of the Competitor . If a slightly longer magazine was needed, rather than make a baseplate with that extended hollow section why not put a 2+ basepad on it instead?
I've never heard anyone complaining about having too many bullets in a magazine, except maybe Joe biden, and I don't want to turn this into a political rant.
Good question. The (extended) baseplate on the Competitor has an "open" bottom well you can stick your thumb in (from the outside). That sits (holds) the "normal" Floor Plate Catch (that holds the spring bottom) in place. The Floor Plate slides off of that, like a normal M&P magazine does. So, it's interchangeable with other/most M&P FS double stack Mags.
My guess is, it's a "Bumper/Buffer" for mag drops to "save" mag damage while on the run swapping mags.
Here's the "good news" part. IF BY CHANCE, you just happen to have one of the new S&W M&P FPC 9 Foldable Carbines, those 23 round mags that come with that (2-23 round & 1-17 round), WILL also work in the Competitors Magwell Flare, you HAVE to remove the grip adaptor (spacer), just need a good palm slap to make sure it's seated. Better EASIER fit with the Magwell Flare removed, snaps right in has a very small gap, has the distinctive "CLICK" when locked in place and good to go, 23 rounds.

Yes, 23 rounds.

It does almost double the length sticking out, but it's also 6 more rounds, still all metal mag tube.
The 23 round mag has it's own (different yet) Extended Floor Plate that is taller up the side of the mag, but "normal" thin floor plate. Still swappable with the "Bumper/Buffer" on the Competitor IF you still want that, but makes it even longer in length.
In time, we should be seeing OEM 23 round mags for the M&P FPC 9.