Additionally, landlords don't benefit from the higher prices (ie. market rate rent) either, since that also pushes house prices up. A landlord entering the market has a higher capital cost that absorbs the higher rental return, such that typically rental yield remains about the same (at slightly higher that the cost of capital that covers their increased risk compared to a more stable investment).

Those who benefit are those who own housing at the time of market rate increases. That's just regular investment return and the risk/reward can be directly compared to any other form of investment. Current owner occupiers and current landlords benefit at the time of every increase (even if their capital gains are not immediately realised). And then every household, whether they are owner occupiers or tenants, have to pay in the form of higher capital expense. Landlords simply pass the higher rent through to pay for their higher capital expenses.