what has been said in this forum is :
Ripen inside but NOT necessarily in window(meaning direct son light). BUT on the counter, your dinner table .. or anywhere without direct sun.
I have been doing this and it works fine.

Agree that you don't want them on the window, don't want them in direct sun. When we say ripen on the counter that doesn't mean in the window or the direct sun.

Can't say why your Grandmother thought the window sun was needed.

Dave

Because everyone thought the window sill ripened them due to sunlight ,theY did not know any better ,kinda like they thought small pepples in the bottom of your planters increased drainage