I don't see it as a favour.... I see it as what they're meant to do. It states the timeline for international flights for interlining and baggage allowances on the connecting flight. I have a number of first baggage tickets in my case and could've asked to put them on if required or asked. I think it's quite clear on the website of the baggage allowances. There's also the advantage on not having to collect the checked bags so was able to come straight to LAX first lounge for lunch.

No idea of BA's policy but if I couldn't go in, I would've stayed in the AS lounge.

https://www.alaskaair.com/content/travel-info/baggage/checked-bags

Regards,

Michael