The 5135 spars are black. If it follows the same pattern, that means the gundeck will also be black. THe surrounds around the faux cannon tips appear to be black.
To me, the 5135's hull, bowsprite, masts, spars and cargo-hatch seem darkbrown; same colour as the masts/spars/sprite of the 4290.
A darkbrown hull would also give some contrast with the black gunport-hatches.
The "faux gunmouths' surroundings" seem indeed black.
So it is possible the faux cannon surrounds are NOT unpluggable, because they may actually be integrally moulded as PART OF THE GUNDECK.
On the 3286 gundeck, there are pegs for the cannons to snap into place when they are sticking out of the port holes. I can't imagine how those pegs would be sufficient enough (unchanged) to accommodate faux cannon plugs that are removeable. I'm going to guess the faux cannon plugs are a new mold design incorporated into the gundeck in place of the pegs (why would it need pegs for cannons, when there are faux cannons to take a real cannon's place?)
I've been reflecting about those pegs that held the canons in place on the 3940/3286, and possible "faux gun"-plugs or not...
Instead of using the pegs near the floor of the gundeck, they could add 2 such or similar pegs to the inside of the hull; one peg on each side of a gunport. That could hold "plug-in faux gunmouths" well I think.
If the "faux guns" are unpluggable and would be part of the gundeck's mould now, then they would have to use more plastic in comparison to adding a few plugs to the inside of the hull. They would need to raise the height of the sides from the inner gundeck to the same height of the upperlevel of the gunports, almost over the whole ship's length. If they just would raise the hight of the gundeck-mould near the gunport positions to include the "faux guns", these "faux guns" would be quite "wobbly" I think, and then that wouldn't guarantee the sealing of the ports to keep water out (one major advantage of "faux guns").
Just my thought...
I'm hoping for "plug-ins"; that would leave all options open and make everyone happy.
If you like them, you leave them on the ship. If you don't, you replace them with the proper guns.