I don’t think there’s any guarantee this will be true for AS Basic Economy. We used to be able to use GGUs on any fare. Now G,T and R are excluded, so AS is willing to chip, chip chip Gold benefits based on fare cost. I think it is a sucker bet that R fares/Basic Economy will be “no waivers, no favors, fly it as booked or lose the fare”. I guess you can cancel and rebook INTO it that way... and lose upgrades, changes, quite possibly more, but it might be a "roach motel" kind of fare.