I think this is the ideal scenario. The couple need to get to know each other away from the pre-established family situations. If the girl moves in with her in-laws, she’s the new element - the in-laws continue to do everything as they always did and any changes to the family dynmamic are attributed to her.
If the couple live alone, they establish their own household with their own routine.
After a few years when the couple move into their own home, then they should invite his parents to live with them because the parents when they’re older do need the support and companionship of their children. Another big consideration which most guys don’t clue into - if the DIL moves into her in-laws place, the MIL will already have her home running according to her routine and decorated to her taste - the DIL never gets to put her mark on the home.