I noticed this for sometime now and also noticed how it works correctly on other wikis. So I think this is not a MobileFronted's fault, but a problem with the design approach of English Wikipedia.

The message is MediaWiki:Protectedpagetext message, and is a very simple message in its default form but most wikis have replaced it with longer dynamic messages. English Wikipedia, notably uses a web of elaborate templates to produce that message. See some parts in Template:Protected page text and Template:Protected page text/semi

Particularly, MediaWiki.org uses almost a similar design with enwiki and it displays well. French Wikipedia uses design, but took a different approach, and it works too. Spanish Wikipedia uses a much simpler design.

MediaWiki.org	French Wikipedia	Spanish Wikipedia

MetaWiki, Arabic Wikipedia and a host of others all copied (or mostly copied) from English Wikipedia's templates, and they suffer from the same problem.

https://en.m.wikipedia.org/wiki/MediaWiki_talk:Protectedpagetext is the problem. This needs to be fixed on wiki.

<ignore>
Looks like edit is in sandbox mode still https://en.m.wikipedia.org/wiki/Template:Protected_page_text/sandbox

@Jdlrobson the sandbox change was pushed live in https://en.wikipedia.org/w/index.php?title=Special:Diff/962915348

I think the 2 column layout on mobile is still very problematic:

That should be discussed locally, the community may prefer to keep both the h2 headings visible as long as possible, even if it will make narrow columns. Local discussions are welcome at: https://en.wikipedia.org/wiki/Template_talk:Protected_page_text