One effect two years ago was 3x retina images for first iPhone 6 Plus, roughly doubled size of all asset catalogs. With app slicing the 3x aren't usually downloaded to most devices, but that's not clear to customers.
Around the same time was the 64-bit requirement for app updates. This resulted in a dual-slice fat binary. Began being enforced in June 2015 I think, so about 2 years ago.
App Thinning handles that issue too.
It dies but store lists full fat binary size.
Probably Apple lifting size restriction.
It not approaching the 4GB limits, its an addition of 100MB.
It looks like Facebook was already over 100MB when the bump happened, so it must have been something else.