Strange that your service guy recommended that you open the low point drains after filling the system with RV antifreeze....I understood the entire concept was to fill all water tubes and pipes with the antifreeze to dilute/displace water in the system. Were the valves on your low point drains factory installed on your rig, or aftermarket? Did you have four (4) low point drains total?

I was under the impression you should open the low point drain when the plumbing is under pressure with anti freeze until the anti freeze comes out and then close. This ensures the pipe to the low point drain and the valves now contain anti freeze.

all factory installed, 4 in total

Drain all your lines of water at the low points, close them, pump the pink juice to all faucets by opening each 1 at a time til pink, leave the pink in the lines & do not open the drains once filled.
Also pour & leave about a quart +/- in the toilet, a cup or 2 down the bath sink, shower drain, wash machine line if no wash machine, your kitchen sink probably doesn't have a p trap but pour some down it to get in the tank.
Doubt very seriously you have 4 low point drains, you will have 1 each hot(red)/cold(blue) drains , 1 fresh water tank drain (probably blue) & 1 fresh water tank vent (probably white). Regardless of what your service guy told you, if you have a drain for your ice maker either the previous owner added it or you have the only RW ever built to have one.
Any further winterizing questions you should ask here as your service guy has given you poor advice in my opinion.

Isolate the water heater using the bypass valve. Remove the anode and drain the water heater, put the anode back in in just enough to keep the critters out.. Open the freshwater tank drain and empty it, close the valve when empty to keep the critters out. Remove the element from the water filter housing and replace the empty housing. Open the low point drains, turn the faucets and shower on so the water drains properly. Unhook the ice maker water line at the solenoid. When the system is empty, close the faucets, shower and ice maker supply valves. Hook up a compressor to the city water inlet and blow air out the low point drains until they're done misting. Do the same at each faucet, shower, toilet, ice maker line, outside faucet etc. until they don't blow mist from them. No need for antifreeze. Follow the fridge manufacturer's directions for winterizing the ice maker and dishwasher. Where you have conventional drain traps, use some mineral oil to fill them. No need for anything in a Hepvo trap. Antifreeze will evaporate from the traps, and cooking oil on top of the antifreeze can turn rancid while in storage. Just my way of winterizing mine. Been using air and no antifreeze for 5 years now without any issues. I also don't have to flush the system to get the antifreeze foam,taste, and smell out. I do sanitize the freshwater system with a 1/4 cup of non scented plain old household bleach to 15 gallons of water water each spring.

If in extreme cold blowing out the lines may not be enough, but is a good idea before adding antifreeze & a couple gallons of RV antifreeze pumped into the system is pretty cheap insurance.
Never heard of the mineral oil idea in the traps, but have used vegetable oil poured into the waste tanks to help slick up the valve operation.
In the cold temps I doubt there's much evaporation happening or at least never noticed it in my rvs. As stated I pour a quart or so in the toilet & come spring there's still about a quart there.
Once you've winterized a couple times you'll come up the method that works best for you.

I can't see how one could have an issue with freezing if all the water is blown out. There wouldn't be anything to freeze. Worked fine for us in the military,and we were in places colder than any RV should ever be in.

I can't see how one could have an issue with freezing if all the water is blown out. There wouldn't be anything to freeze. Worked fine for us in the military,and we were in places colder than any RV should ever be in.

I mentioned this only to info others!
RV antifreeze is cheap insurance if by some chance all the water didn't blow dry.
By all means if you & the military are good with just blowing them out then do so.