Sure, that's a truth .... and if it's time to change like at end of your season ..... but OP is past that point now .... but he can do it tomorrow ..... which is still better than 6 months from now.
I never heard that one.
You gonna start a cold bike to warm last season's dirty/acidic oil that is gonna drain the same this time as it did last time you shut it off hot just to get some last bit that is maybe fell out of suspension in the bottom of the crankcase .... with the hope being to get it suspended again maybe ???
If it's something up on the sides of the motor's internals, it's no more likely to get swept down below by a warm up than it was at end of last ride? If it's something that fell out of suspension in the bottom of the crankcase / trans floor, I think it likely the oil flowing out the drain will get a bunch of it anyway.
) it far better to just do the drain if it's already cool .... and put in fresh oil & filter .... and then if you think you want to start it .... start it then with fresh clean oil and new filter
which will filter that stuff out and
fill all those galleys and passages with that pretty clean stuff.
The only reason for a warm up before change that I've ever heard
is to speed the drain like "I want to change my oil now" so that cold oil isn't left slowly dripping from high places like it would if you just started it and moved a few feet to where you were gonna do the change without a complete warm up .... and because a start without thorough warming leaves condensation all inside the motor and exhaust as it never get's hot enough to eliminate it.
Unless I have some other reason to have the engine running .... like maybe I did just finish a ride (or drive if cage or mowing the yard if tractor, etc
) .... I've always dropped it cold and allowed it a long drip time. There's always other chores.
Anyway ..... everyone has their habits, reasons, preferences, etc ....
.... and them's just some of mine.
Stay Warm Y'all!