Once when I was in an RPG shop I visited frequently, some youths came in and said "We want to order 5 figures." After a short pause they added "Can we get them cheaper, because we're buying 5?" The shop owner said "Fine, I'll give you one for free." They said "No, the other owner promised us 10 percent". After a small pause the shop owner smiled and said "Ok, I'll stick with the promise, you get 10 percent."
Percentages suck. They feel almost designed to confuse. Just about anything is better, really. Doesn't help that people using percentages either use them intentionally to confuse their victims - think shop owners, advertisers, banks, scammers, especially in finance and insurance adjacent areas - or just don't realize how easy it is for everyone, including them themselves, to lost track of the base/referent.
I've come to see the use of percentages as a warning sign.
Great satire, I think the greatest satire is one that sounds totally real. That which lets the reader think twice. But "I've come to see the use of percentages as a warning sign." gave you away.
They're both percentages. Using the wrong term isn't a math failure, like in your example.
"markup" versus "margin" is an arbitrary choice, not something people should be expected to intuit. And they're usually close in value, so people are less likely to be informed or reminded of the two terms and which is which.