Ironically, on the advice of one of your WHALES club co-members, just tonight I tried to take the inner hose out of a 24" water heater supply line to build my MLT. Talk about a royal PITA! I was able to get the hose out of a typical SS supply line in about 3 minutes. After working on the water heater supply hose for I guess 45+ minutes I gave up (I had about 4" out by then). I'd love to know: How do you do it? There's got to be a trick I'm missing (beyond the typical "push don't pull" advice).
Try warming the hose with hot water and then slather it with dish soap for lubrication. I had no trouble at all removing the braid from a 3/4" water heater hose. The soap really helps a lot.