To be fair while this statement is ill advised, I think people are misinterpreting it. I think Sancho is focusing on the people stirring up shit about Ten Hag's comments rather than criticising Ten Hag. Like we see Ten Hag saying he's not up to standards in training and people are (understandably) then saying he's lazy, not putting effort in etc which is probably infuriating for Sancho.
He shouldn't have made this statement but I think it's not aimed at the manager hence the ending paragraph. I don't see this as the doom and gloom statement and drama that most here seem to. Just poor wording. Like you can really tell he wrote this himself rather than his PR team doing some generic copy and paste bullshit.