I imagine he's had 10 month plus spells without injury for most of his career, just as Matip had before he came to Liverpool. Matip managed a full season last year and Keita managed 10 months. We obviously do need to manage them more than players like Salah who are always available but to suggest he's going to break down every 2 weeks is obviously an exaggeration.
Is it?
Admittedly doing this off the top of my head, but he missed around 40-50% of the games in his first season - was it three separate injuries?
He then had a slightly better 19/20, where he still missed games, especially a lot of the first half of the season (which is where we actually won the league), before playing a lot in the last couple of months after the covid stoppage.
Then he barely kicked a ball and missed most of 20/21.
Last season he had his best availability, 'only' missing about 8-10 games through injury.
Now, he's gone for the first couple of months of this season.
It's not constant absence, but simultaneously I don't think anyone being sick of his lack of availability is exaggerating in any way.
Edit - having checked his injury record on transfermarkt, it doesn't seem to make sense. For example, it claims he missed 23 games through illness and injury in 20/21, but he only played 500 minutes in the PL that season and 147 minutes in the CL, so in reality he missed a lot more than claimed.