Problems with flow around initial large character on newyorker article

The initial character (P) of the article is large, and text is supposed to flow around it. In Nightly (haven't checked others) it doesn't properly flow around the P; in Chrome it does.

A quick test of 69.0.1 shows it flowing correctly around it.

I can reproduce on Nightly75.0a1 and Firefox74.0b3 Windows10.

STR

1. Open https://www.newyorker.com/sports/sporting-scene/is-stealing-signs-in-baseball-really-so-bad-bobby-valentine-has-some-thoughts
2. Scroll

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=4ad2150e73c0b19f1f6264a4b9ad6927986d43ce&tochange=37e0bd919af057d44c5c1410458c0f00a3653c11

Setting layout.css.moz-document.content.enabled = true fixes the issue.

I can also reproduce on macOS.
Toggling layout.css.moz-document.content.enabled also fixes this issue for me.

This is likely a duplicate of Bug 1376061, which is masked/worked-around by some extra styles that the site provides in a

@-moz-document { ... }

snippet (which we ignore in Nightly).

I confirmed that the current stable release (Firefox 72.0.2) appears to do the correct thing.

There appears to be strong evidence in the attached devtools screenshot that this is the same bug, given the p.has-dropcap::first-letter and the float: left;