I noticed that https://en.m.wikipedia.org/api/rest_v1/page/mobile-sections/Barack_Obama/ is returning giant tables which are never shown on mobile. iirc these are stripped on MobileView, greatly reducing transfer size for many larger articles.
On the Obama article the "This article is part of a series about..." table is one such example:
(screenshots are from Desktop - on mobile we're sending these giant tables but there's a min-width media selector which keeps them hidden)
So are the giant tables at the bottom of the Obama article: