Warmed up oil flows around easier. Some folks still check oil with their bike on the side stand instead of it being level.
Mother Honda, being a corporation that didn't want suing, had to do it as an idiots guide type procedure - that probably sums it up.
Leave it on the stand, give sufficient time for the oil to drip, make sure it's between the high & low marks, and job jobbed. Doesn't matter really if that time is 2-3mins, or 2-3 decades, the oil level will be the same (unless you have a leak). Note, if you're leaving it 2-3 decades between changing oil, you're braver than I, and I would suggest you only check the level of the new stuff you're putting in, rather than the old stuff.