IMO there is exactly 0% chance Sadio Mané plays his last game in Cameroon at 6pm (so he'd finish at 9) on the 18th, jump on a plane for an 8 hour flight, get to the UK at 7am on the 19that the absolute earliest and then play on the 20th in a semi final.
Also Senegal are one of the favourites so it's really unlikely anyway.
He probably said it because it is what happened and it's frustrating for him that 5 players isolated for a week for no reason and the fixture congestion is now getting really bad for them.
No one is getting back on the pitch any sooner, there's no benefit to liverpool from telling the world they were false positives instead of real ones.