[xxbondsxx]

Yes they are, in a sense that the outstanding mortgage debt grows at a slower pace than inflation.

However the 3% is guaranteed for ~30 years, so it's likely the bank would still come out ahead in the long run if inflation settles down. It's also not an infinite money slot machine -- you can only qualify for so many mortgages (which require large down payments) and houses are pretty illiquid assets.