Yes it does. Silent payment addresses, lightning invoices, and lightning offers all have an HRP (
sp1,lnbc1,lno1). I included this in my examples.
Ah, apologies, I misunderstood the point here to have one parameter. Indeed, we could, however that may break existing implementations. BIP 21 as written would allow this, but not sure if any existing implementations try to parse parameters as K/V and fail if there’s no =. Its nice to avoid a few extra characters in QR codes, but not sure its worth that risk.