Oh yes they are! :-)
Initially, yes, but..
That's all very true, but nevertheless it is also true that real time rental yields are determined by a property's real time value (and by the rent achievable, obviously).
Yield and gearing determines the investor's overall return, and in a hypothetical situation where actual rent on a property remains constant but the property's value goes up and down, then clearly yield will go down and up, affecting the investor's return. The investor, noticing that property value is rising but achievable rent is not keeping up, will have to make a commercial decision whether to smile because rising value is boosting his potential return in terms of future realisable gains, or to frown because he realises that he could make more money by selling up and investing the proceeds in something with a higher yield.