You aren't entitled to anything in a room description until you have a room, you don't have a room until you check in and thus any benefits cannot start to be reasonably delivered until you have checked in this is just obvious and fully consistent with the policy.

The Grosvenor House is a 2 Tower property. All tower 2 hotel rooms include Level 5 lounge access. Tower 1 rooms do not come with inclusive lounge access. The property does not typically upgrade to Tower 2 from Tower 1. The rates that come with inclusive transfers (bar one room type it appears, which does not confer lounge access) are for rooms in Tower 2.

It would be perfectly possible for this property to treat Tower 2 as a "Towers level" and not allow any upgrades from Tower 1 to Tower 2 nor give Level 5 access to Tower 1 guests. Be very careful what you wish for.