Hi KarenJ168,
I think you may be mistaking width for length because none of their mattresses would be 4" out of spec. A “standard” king size mattress is 76" x 79.5" +/- 1" so the 74.5" width that was mentioned in the earlier post was referring to the width of the king size not the length (which would be the same for a king and a queen). A “standard” size for a queen would be 60" x 79.5" +/- 1". You can read the the ISPA (International Sleep Products Association) standard sizing for mattresses in post #2 here.
When mattresses are compressed it can sometimes take a few days to regain their full dimensions and this would be more common with king size mattresses than other sizes because they are “squished” in width before they are compressed and roll packed (see their video here).
BB did have some issues with a small number of their mattresses not expanding back to their full size over a year ago (see the end of post #115 here) but that was related to the gluing and compression process itself and only applied to a very small percentage of their mattress that were made over a short period of time (usually in king size) so it’s possible that you were reading some comments from that time. It has long since been resolved and the few customers that received one would have been able to exchange their mattress for a new one.
If for some reason you were to receive a mattress that was clearly “out of spec” then they would certainly look after the issue for you and of course they also have a 120 day return policy so if you are unhappy with your mattress for any reason then you can just return it for a refund.
Phoenix