I'm not so sure that's what he means. If you look in the comments, the OP says "Ah yes. I should have pointed out that this article only applies to PhD programs in the US (in Computer Science). ... A UK PhD, for example, is rarely seen as equivalent to a US-based PhD, precisely because it is so short and does not typically involve coursework."
For the universities I applied to, you are still required to take classes in the PhD program. Even if you already have your Master's and decide to go for a PhD at another university, your class credits may not transfer (in fact, I was told at a graduate visit day at UMD that they don't accept credit from MS programs other than their own), so you might even have to do the required coursework all over again while going for your PhD.
Personally, I was able to find a graduate research assistantship my first semester here at UMD, whereas most of the incoming PhD students are in teaching assistantships. I feel like I'm getting a good taste of how research/the PhD program.
>> I was told at a graduate visit day at UMD that they don't accept credit from MS programs other than their own
I don't know how common this is.
I know lots of people (probably most) that get their Master's at a different place than their BS, but don't know any that got a PhD at a different place than their Master's - maybe because as you say the barriers to moving are too high. People that aren't happy where they got their Master's don't get a PhD at all.
For the universities I applied to, you are still required to take classes in the PhD program. Even if you already have your Master's and decide to go for a PhD at another university, your class credits may not transfer (in fact, I was told at a graduate visit day at UMD that they don't accept credit from MS programs other than their own), so you might even have to do the required coursework all over again while going for your PhD.
Personally, I was able to find a graduate research assistantship my first semester here at UMD, whereas most of the incoming PhD students are in teaching assistantships. I feel like I'm getting a good taste of how research/the PhD program.