I don’t know anything about Flowers’ injury woes because aside from his rookie year, I have not noticed them. Hollister has seemed to battle something or another on a fairly consistent basis throughout the summer and first game. He missed most or all of the preseason and was finally taken off of the injury report on 9/14, but promptly placed back on it again, this week.
Hollister played in the first two preseason games. He caught 2 of 2 against the Skins, and 1 of 1 against the Texans. According to my notes, he apparently tweaked something (probably the hammy) either in the HOU game or early in the following practice week. After that, he was participating in warmups, some positional drills, but spending "team time" on the lower field. So, he "partly" missed only the last two weeks of Camp.
So far during the regular season, Hollister was "limited" for all three week-1 practices (hammy) and didn't play against the Texans. Last week, he was "limited" (hammy) for the first two sessions, but off the report on Friday. He caught 3 of 3 against JAX.
This week, he didn't appear on the report until Friday, after apparently suffering a "chest injury" from a "hard landing" in Thursday's practice.
In contrast, Rowe missed 7 games in 2016 with various lower leg issues. He then missed 8 games last season with a groin issue (apparently re-injured now). To me, THAT is "oft-injured". I don't apply it to players who occasionally miss a game due to something that's not likely to be chronic (ribs, chest).