I'm aware of that. This is why I tried hard this week to receive PBS tps. I am receiving AMC 21 very well: stable SQ 70% from Claro which uses DVB-S2 also. There is something different about the PBS tps. I will conclude that using only the actual signal power at a particular receive location is not enough to determine if you will or won't receive a tp. I have never seen tps that supposedly could be received with an 80 cm dish that were so difficult for me to receive. For example, 123W supposedly needs a 100 cm dish. I was able to find 123W quite easily and all tps blind scanned in with reasonable SQ.
Earlier, I thought I had an LOS problem. I don't think so. If LOS was an issue, I would never receive Claro at 70%. I might receive it, but SQ would be down or unstable. I could see as I panned my dish slowly east/west and up/down that I am dead centre on Claro. I then checked and I could tell by carefully watching how PBS affects the SL and SQ bobble head that I was also centred on the PBS tps.
Inverting the dish was a good idea since it allowed full freedom to pan the dish up and down to be sure I was centred elevation-wise. By the way, this autumn season seems to be the best time of year to search for new satellites. I think it's the dry air here when the weather is sunny that is delivering maximum SQ on all satellites.