Seems highly unlikely that an LHD can hold six of lcac. Type 726 measures 33m x 16m. A ship that carries six of these will be way heavier than 30000 tonnes. Even if the ship uses its entire lowest level as a dock(unlike the above pic which seems to divide functionality of lowest level between various types of storage), it'll be quite a stretch to fit 6 of those behemoth 726 into the dock. (Bdw, does somebody have a picture of 4 type 726 inside the type 071?, i've come across various pics showing 3 of them inside the dock but had a doubt about its official statement of fitting 4 lcac).
4x LCAC in each 075 is probably a reasonable number.