....... You can't fill a pressurized tank with a liquid gas without giving the air someplace to go and it goes out that valve. ......
Not really true
You can fill a LP Tank with out the bleeder valve being open - but on MH tanks it is difficult to weigh the LPG Tank and some (a few) RVs do not have a gauge so this valve is used to give an indication when the tank is 80% full and is often called a "..80%..valve".
My 500 gallon stationary LP tank is always fill without using its valve being open but is filled to 80%, as indicated by its level gauge. The same is true on all LP Tanks - for example portable tanks are usually filled on a scale (filled by weight) and LPG as is not usually vented during a fill.
And there is no need to give "...the air someplace to go... as there is no air in the LP tank. The filling is done under pressure without any need to vent.
phe