Those bitcoins (the ones being held by third parties) are never censorship resistant from the user's point of view, since the third party holding the coins can choose to refuse to sign any transaction they want (not to mention simply make off with your bitcoin at any time). Bitcoin itself as an entity is no less censorship resistant, as the owner of the coins in the third party wallet (which is the third party) can still broadcast any valid transaction they like and the network will broadcast and mine it.
If users choose to give up their censorship resistance, their privacy, their security, and all the other benefits bitcoin brings by giving their bitcoin to someone else to have ownership of, then that's their decision and their loss. But it doesn't change the bitcoin protocol, and the person or entity they give their bitcoin to still has the same censorship resistance, privacy, security, etc. as any other user.