Is this really a thing? Tipping up the plane
 

Yesterday I exited an EasyJet A320(?) at Birmingham. I was sat at row 12. The plane only had the front steps fitted (took Swissport 15 minutes to bring the steps….). By the time I got to the exit the cabin crew asked everyone to wait in the galley until a few more people had come to the front of the plane. There were mutterings about the plane’s centre of gravity. Surely there isn’t a risk of something bad happening in this situation is there?

Planes get tipped on their tails far too often but usually in cargo operations when someone forgot to fit the tail support. Just have a look at any airliner from the side and see how long the tail "lever" is relative to the landing gear position.

Probably an A319. The bags etc are loaded in the aft cargo holds for performance reasons (nose down trim).
If someone has faffed around and thus had a delay in moving people forward AND the baggage handlers are late/delayed then it is possible to get a nose light situation.
First thing that the crew would notice is the distance to step down to the exit. Next thing would be an alert from the flight deck saying the nose gear is at full extension.
:)
The A320 is longer and to prevent the above, luggage is loaded in the fwd holds. :)