Though this is the normal construction: noun + verb + "-er", like the "firefighter" and "naysayer" examples in the thread, whereas the tweet's claim is that "exocentric" coinages with form: verb + noun, such as "pickpocket" and "spendthrift" where the verb comes first and there's no "-er", date from 1550 to 1700 almost exclusively.

It feels like there should be a modern counterexample, but I admit I can't recall any. "Runmouth" would be a near miss, but it apparently refers to a personal quality rather than a person. Perhaps a resurgence is possible with words like "baitclick" and "postshit"?