L3 is easier to sell if the frame doesn't work for you. As for grip size I think having 3-7mm gap (one whole finger is too large imho) is ideal. The acid test is how badly you get callouses with a smaller grip size. Play with both sizes and see what callouses develop. Sizes among brands are also different. I find Dunlop, Yonex, and Prince slightly bigger than other main brands, but I haven't used all the brands.
For sure Prince grip sizes have increased over the years. In my younger years I used L5 with an overgrip (Prince Pro), then for many, many years used L4 (Prince Scream, Thundercloud, Shark, Tour 100 etc), then went to L3 when L4 grip size was not readily available, such as Exo3, Phantom Pro.
On all these racquets I've used an overgrip and the gap between my ring finger and palm has remained at 2-3 mm which I find ideal.
I picked up a Prince Phantom 100x a few weeks ago at a bargain price and it was a L2. Amazingly, after adding an overgrip, the gap between ring finger and palm is still 2-3 mm!
So absolutely, Prince grip sizes have definitely increased over the years - my hand is still the same size and I still have the majority of the above racquets to compare.