very useful information. would you mind (or another poster?) confirming if DMs can indeed grant access in this manner remotely?! to people not at the airport at the same time as me? amazing if true

I am familiar with the other method, which is someone traveling at same time as me but non-OW airline. I've done for people in HKG flying a bunch of different airlines, top of mind includes Eva and United recently. At airport same time, I advise lounge I would like to purchase access for guests who I am not able to guest in due to lack of OW airline boarding pass, and they charge 15k Asia Miles per guest via paper voucher right there at the lounge. (They still scan the guest BPs IIRC, but it doesn't matter.)