I doubt very much that you are clumsier than any of us : To be honest , when I took of the tank it was to fit the piggyback ECU . I anticipated that operation and rode the bike on nearly empty before that . Taking of the fuel line from the pump does produce for an instant a spray (pressurized ) of fuel . I rested my tank on a garden variety plastic bucket with the pump attached and the infamous rag in plastic bag . Fuel smell , yes but no fuel spilling / leaking as such .I must be clumsier than most, or maybe I needed a helper but the tank sloshed plenty as I was trying to remove the fuel lines etc. and the plug I used leaked.
With a gas fired water heater in the same garage, I don't want to take any chances. 40+ years ago I burnt a garage down because of a fuel spill! Hard to forget something like that.
So , like you say having a gas fired heating on and considering what you went through 40+ years ago I can understand your concern .