Possible that the player misheard a strong scouse accent but it wouldn't explain how scouse coppers misheard. I think it's unlikely that Manchester police were on duty.
Mirror journalist has tweeted to confirm his story and Guardian has also confirmed that players were arrested on suspicion of racial abuse
Oldham's Tom Adeyemi suffers 'racial abuse' in Liverpool FA Cup tie | Football | The Guardian
"Suspicion of" is the key. Let's wait for the facts.