Who cares how you do it as long as the end result is the same. RV antifreeze is non-toxic and floods the entire system. Blowing air "up" or through a tube always leaves a chance air can slip by the water...leaving it untreated to freeze. Same principal as drinking a milkshake with a straw....you'll get the whole glass empty, but gurgle the last few drops till you pass out from dizziness...and never get it all.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie