IIRC the configuration that allows hidden volumes is distinguishable from the basic configuration, so they could tell if there's the potential for a hidden drive to exist. If so, they could assume the hidden container exists and throw you in jail if you don't produce a password that unlocks one.
If the format schemes are indistinguishable that's good news.
IIRC free space on the outer volume has to be continuous―normally at the end of the fs. I.e. the volume will look like it's not used too extensively. Which I guess may or may not look suspicious depending on your claimed use-case.
If the format schemes are indistinguishable that's good news.