sort of. the only difference is that the optimised version might even be less than 7gb although that sounds about right*. the phone only optimises when it needs space. if you open loads of photos and videos on your phone that 7gb will go up, as it downloads full versions, but only whilst you have tons of space. if you needed the space it would go back down as the phone would delete the full versions again.
*basing that on my own phone has 3.17gb of photos and icloud has 38.7gb but then again its a new phone with lots of space. i am sure that would go down to under 2gb if needed.