You either compared incomparable things to begin with or ended up with a scalar value when you divided them. Units can be divided, too. The slash in m/s is there for a reason.
We'd do better to stick to the original point: that both partners should do their best rather than a half-ass job. A point I happen to agree with. Numbers just get in the way.
I admit it is innumerate slang to write "50/50" when really it means "(item/effort/task) is split 50% among 2 people" ... so given HN's general level of math ability, I should have phrased it better.
While 100/100 expands to 100/100:100/100 , or 1:1 of course.
You might say the ratios are equivalent, but of course, you have ignored the units (if a relationship can have units).