Likely a ding, but probably not too big a deal in the grand scheme of things if the person is now off it. It certainly could impact some sites, but no application is perfect and a million other things could have a similar effect. With timelines in particular, people vary tremendously in whether or not they view it as important. The old guard (particularly on the academic side) tends to think the increased emphasis on timelines and getting students in and out quickly is silly. Whenever we expressed concerns about wanting to get finished, one of my advisors invariably mentioned the norm was 7-8 and 10 was not unheard of during his grad school days (he got out in 6 and apparently caught a lot of flak for it).
That said - I assume the person has checked with their department that they need to reveal this information? I know my department had an "unofficial-this-is-not-probation-but-it-could-be-soon" status that was utilized before people were put on "official" academic probation. The former did not need to be disclosed on things like internship apps and was usually used for things like timeline violations or other technical things, with the latter being reserved for serious issues (e.g. academic dishonesty, a student not getting their act together after being put on "unofficial" probation). Kind of gaming the system a bit, but its how things were done at my school. Wasn't relevant for me and I never even knew it was being done in that way until my DCT brought it up at an internship prep meeting.