It's a little screwy, because you're getting paid the lenders instead of the borrowers. But it's still fundamentally no different than a bank that borrows at 2.5% and writes mortgages at 3% APR.
I guess you could argue if the bank is not paying interest on that money, then they won't lose anything if the client is in default. I think there's probably still opportunity costs to the bank in that case - they could be loaning that money to a client that pays additional fees and makes the payments on time. But I imagine they would still foreclose and sell the asset to recover the principal in that case. Which might turn a profit for them.
Where APR is the effective rate including fees.
If I was to refinance to a 30 year mortgage with the same bank/mortgage lender this quarter I would get a 0.5% mortgage with 'bidragssats' at 0.6812% so around 1.18% effective rate. This would also increase my principal by ~30000 DKK or around $5000.
The interesting part is that that this rate can be changed over time to whatever the lone-shark wants it to be, thus - as always - you need to look at the TCO.
ÅOP as it is in danish: "Årlig Omkostning i Procent" - aka the Yearly cost in percent...