I'm 99% sure they are the same.
By coincidence i've noticed quite a few scenics lately with the 'flaps' missing showing the petrol cap itself.
Has someone broken yours off intentionally?
I thought the Megane has a circular flap? the Megane Scenic has a square flap
The 1999 to 2003 phase 2 flaps are p1ss weak!!
when I got my 2001 Scenic the flap was missing. I got a replacement which after a few months came away in my hand!!
as I opened it! I don't put petrol in the car very often either as I run it on LPG. High demand means some car breakers are asking £30! for a flap.
the earlier 1996 to 1999 phase 1 are much stronger and heavier in design and they are interchangeable thought the locking plungers are at different heights so don't lock but as I never have more than 1/4 of petrol I'm not to concerned and I paid £8 though it is the wrong shade of blue.
It's the same story with boot lock buttons the phase 2 ones fall out for a past time the phase 1 is much stronger so I have a phase1 boot lock on my phase 2 seems like they where redesigning to reduce production costs? and unfortunately compromised the quality!