If they're flying on the Avios, they're not building up mileage liabilities (granted, there's not actually a problem with mileage liabilities: they're ultimately closer in fact to non-voting equity than anything else, much like the "debt" of a sovereign (not to get into a debate on MMT)).

At the luxury hotel level, the commission on the booking gets into the range (about 10%) where BA's gross profit from £x of hotel is not that different from the EBITDA from £x of flights (and considering cost of capital, it's more like the profit from far greater flying revenue), without even getting into how being capital-light supports all manner of moves to enrich shareholders and management (regarding which my comment is "hate the game, not the player").

If BA gets into a situation where they need to get BIS, they'll adjust Avios or TP earning to promote that, and in all probability most who swear up and down that BAC is a disgrace will take advantage (perhaps what was previously a marriage will end up more transactional... far be it for me to suggest that either BA or FTers are like gold diggers, but neither has necessarily much interest in "broke broke"). In the current environment, after so many airlines decommissioned aircraft and the manufacturers have backlogs for years in the future, a glut of S relative to B isn't the problem. Tempus fugit and all that.