Bryan makes up a lot of absolutes in "the videos", many are harmless, many are dead wrong.
You can experiment for yourself. Drain oil on sidestand, replace plug, put bike on centerstand and remove plug again to see if anything much comes out. I'd expect some just because it took a minute or so to change position. Next time do it the other way, drain on center, retest on side.
But really, it doesn't matter. Drain on centerstand without changing the filter and exactly 4.0 quarts is a perfect fill. About 6 oz more when replacing the filter. If you were able to get 6 or 8 ounces more out on sidestand then it would matter, but I don't think that will happen. I don't worry about leaving 6 oz of old oil in my filter. I only change filter every-other oil change.
Have retold the tale many times of my 2000 Toyota Avalon oil changes. Drained hot the oil filter make a big mess when removed. 5 quarts was over FULL on the dipstick. But drained cold the oil filter came off clean and 5 quarts was perfectly 1/8" under the FULL line. Concluded cold drain got more old oil out, which is good. But getting the oil filter off without making a huge mess was what won me over. Darn thing was mounted 45į under hot exhaust manifold and full of hot oil. But was nearly empty when cold.
Hot or cold doesn't seem to matter on FJR. Same quantity to fill either way.
My new F-150 with 2.7EB engine is another issue. Ford says wait 10 minutes to check oil for an accurate reading. Have learned the oil filter needs to be removed before draining because the engine holds a lot of oil in passages even beyond 10 minutes. I have to put it up on ramps to get under to remove access panel, so it effectively "drains on sidestand".
Curious thing, I use a 1/4" cordless impact driver to remove the access panel 8mm head bolts, but the drain plug is a plastic bayonet with o-ring that comes out by hand. Even so this is the most difficult vehicle to change oil I have owned in 45 years.
2018 F-150 XLT SuperCab 4x4 2.7L
2016 Beta 430 RS
2016 Subaru Outback
2013 Tesla Model S 85
2009 Husaberg FE450
1983 Porsche 928S