The Lounge is rated Safe For Work. If you're about to post something inappropriate for a shared office environment, then don't post it. No ads, no abuse, and no programming questions. Trolling, (political, climate, religious or whatever) will result in your account being removed.
I really don't like the "one in __", in this kind of context; it's just not precise enough language, for me.
A back-of-the-mind inference is that each family or grouping of five people has to choose one to stay at home. Even though the reader knows that is not the case, it still fuzzes the meaning, subconsciously (and if you don't know how to write for the subconscious, you shouldn't be writing headlines).
Percentage and fractions have no such implications: "20% of" and "a fifth of" don't conjure any illusions*.
* OK, so who immediately thought "unless you chop people into fifths!"? That's what I mean by writing for the subconscious.
I wanna be a eunuchs developer! Pass me a bread knife!
I think that his motive is pretty obvious - to point out that, in the midst of a world-wide crisis, there are low-lifes looking to profit from it.
And, I don't think any forum (including the lounge) should be above having a discussion about (and even mobilizing action against) such disgraceful profiteers.
You ask what's his motive. Maybe you could tell us what yours is!
I haven't read the Lounge rules, but I'd be very surprised if there's one that says: "do not say or do anything to help your fellow human-beings in a time of world-wide crisis". And, in any case, no matter what the rules were two weeks ago, every Government affected by Coronavirus is currently overturning/breaking them now.
You need to save your jobsworth rule application for a time when there are not more important things to worry about!
Note, for non UK loungers. See here[^] for 'jobsworth' definition.