are they keeping ships to the right scale because the shuttle looks as big as big as the Falcon

Yes, they are being very true to scale. They've gone to the archival models in some cases.

However, some of the things we've grown up thinking were accurate in scale, have actually been wrong for years. For example, the Tie Fighter has been mistakenly scaled in many instances, and this game has been one of the few to get it right.

Watch RotJ again. When they show the hangar in the Calamari Crusier you can see the Falcon beside the Shuttle Trydirium. The Lambda-class Shuttles where very large. Same reason the old Kenner toy was a big toy like the Kenner Falcon.

It seems FFG keeps to the 1/270 scale as good as they can.

A lot of people have asked if the HWK was the right scale but in other threads they say it is according with Lucasarts (or its remainder at Disney, idk)