Older more dominant males could be keeping him in his place and this is why he hasn't crowed yet.
You never know with polish though and I could be totally wrong and you have a pullet there. They are really difficult to sex untill they crow or lay an egg. I have been caught out with plenty in...
:frow
90% you have a roo there. The crest and spur buds make me think this. Do you have another roo?
I'm afraid the downside of keeping polish in a mixed flock is that they are picked on by other breeds.