fdpower,

That is correct. in my experience, TPS as a status is way better than H1 or L1 or any other work visas because it lets you file your AOS without leaving country/without stamping visa. If you never been out of status and have TPS approved and your employer is willing to file your i-140, i-485, i strongly suggest to avoid visa stamping.
Once perm is approved and if the case is strong, my recommendation is file 140 & 485 con-currently (if in regular processing) or if case is average, file 140 first and 485 later. When i was filing from TPS to GC, i wasn't sure because i was not able to find similar cases as reference but now my case is solid example of TPS to GC. My employer was able to save some $ because they didn't have to file L1 petition at all.