<p>Well, LOR’s from profs are VERY , VERY important for admission to PhD programs. And in academia, profs DO know a lot about their colleagues at the other UC’s. So If recent UCLA graduates in your S’ program of interest have NOT impressed the grad school admission office at UCB, then he is wise to go to UCB for UG .
But be aware, the senior prof was serious when he was telling you the Depts position- Profs very often want to teach new students in grad school, and not teach the same students that they had over the previous 4 years. </p>