I've very often seen this leak misdiagnosed as a rear main seal, when in reality it was the rear engine cover gasket. Thing is..you can't really see either until you remove the flex plate. So it'* a close enough diagnosis. However if you go to fix it...I'd suggest having both the rear main crank seal and the rear engine cover seal on hand to save time and effort.
The bolts that hold the rear engine cover on are at a super low torque and have plastic sleeves to align the cover perfectly for the crank seal. The low torque over time loosens up and allows the gasket to leak.
I'm not only the president...I'm also a founding member. =0)
During my last trans swap I took care of this 2-5 drip per night leak.
Here we can see the rear of the engine with the flex and the rear engine cover off. Because we have a one piece crank seal, it doesn't fail often...but it'* a gasket and they can.