I think the idea of a 'bedding in' period is fine. Depends on a number of factors -some on the pitch and some off the pitch. I think with our tactical system, and how our manager tends to integrate new players, he likes a 'bedding in' period. Not with every player but he has done with numerous players. I think the other big factor is the pace and physicality of our league. I wonder if Keita is struggling with this. Maybe the disjointed nature of his appearance, due to injuries, have made it harder for him to get to grips with the different demands compared to the Bundesliga.
That is all completely fair (and with regards to the step-up I completely agree, hence the amusing custom title), but I think we're past the 'bedding in' period a little to be honest. We're talking about a player who we signed 18 months ago, and Klopp threw in from day one once he had actually joined. If he required 'bedding in', why would Klopp do this? Fabinho strikes me as a more accurate example of 'bedding in'. Physically and tactically he was clearly struggling with the demands in England and under Klopp, so he was eased into things. The player himself has spoken about a change in gym routine to build his hamstrings up to cope with all of this. This, combined with a change in midfield shape which clearly suits his game more, means he has now 'bedded in' (or in more logical terms, he is playing well).
Did Leroy Sané suddenly start playing well because he had 'bedded in'? Maybe. But I would say it had much more to do with Guardiola changing system to 4-3-3 and using him as a classic winger, suiting his natural game more rather than playing as an inverted one on the opposite side of the pitch.
Same goes for Firmino. 'Bedding in' may have been a small part of his improvement, but a change in manager and role had a lot more to do with it.
This is probably all a bit pedantic but it just strikes me as a 'momentum' type thing in football: a phrase which people use for things they are struggling to explain. Keita looks like a player short on confidence and struggling to step-up to a higher level of football - not a player short on speaking English or 'bedding in'. If he starts playing well, which I believe he will at some point as there is too much talent there not to, it'll largely because of small tweaks in his game, both by player and manager, not because his English improves or he 'beds in'.