To be really precise even if you used water fittings it would be physically better than a solder fitting. First of all the temperature difference is unique.. the solder will start melting about 185c but the o ring can withstand higher temperature as they are high efficiency o rings same as for gas 630c for 30min your solder is in seconds gone and will cause problems. Furthermore the fittings can withstand higher pressure than soldered joints. 15 -100bar . let me check 10 properties in UK with 50 bat and I will show you how good your soldering is you cannot beat technology
You may be right but you wouldn't be here arguing about a yellow dot. Lol.