I've never heard that before. It will be interesting to see if anyone else comments.
I went ahead and installed the new regulator, the new pigtail for that tank, and the new tank itself. I have the new pigtail for the other old tank, but will need to switch it out when that tank runs out and I replace it down the road. While I had everything apart, I should have weighed the old tank to see how much was in it. But I didn't think of it, and I don't feel like removing the cover and unscrewing the hose now! Maybe I will this weekend.