A basic question about RF multiplexer practical use
You can regard the HMC252 as a multiplexer if you want: -




  So in such a case are RF switches used as well? 


No, you wouldn't use RF switches like the one above for regular low speed applications because regular low speed applications don't need inputs terminating in 50 ohms when disabled. Look at the picture above and note that when any of the 6 RF inputs are not used, those pins are internally connected to 50 ohms.


  So what I understand is that the same RF input is routed to multiple
  outputs.


Or multiple RF inputs selectively coupled to a single output. They operate bidirectionally.


  is this called switch matrix?


It's not an unreasonable description if produced by a marketing guy but I wouldn't use the word matrix because it's misleading technically.