No check engine light? Any fuel work it’s way up there? It is a pretty tight seal on that plug and it must be for a reason other than rattles, maybe?
No issues at all. I've not seen any indication the M3W has a pressure sensor in the fuel system as most autos have these days that would set a code/light.
As regards sealing, any fuel that might slosh up there can quickly drain back via that rather large fill tube, so the seal on the cap itself doesn't have a difficult life. I run a similar Monza type fuel cap on a Lotus Elan which has a much shorter path from fuel tank to filler cap and have never had a whiff of fuel from that, even with a very full tank.
The M3W locking cap does provide a safety function in that should the machine ever become inverted, any mechanical pressure on that fill cap will likely allow it to open. So I endeavor to keep the machine on it's wheels, and should the worst happen, trust those minimalist roll bars will protect the fill cap, if not my head.
