I am going with a typo also. The last (3) bikes that I had, specified both 40 and 50 weight oils. All shared sumps. Quite a temperature range. I can see this for seasonal changes.
I have a Polaris ATV and have owned Polaris motorcycles (Victory), both air and oil-cooled. The bike was specified for 20w-40 weight semi-blend. The dealer was the only place, that you could find the 20w-40. 50 weight oil was also allowed.
I brought Amsoil 20w-50 synthetic motorcycle specific oil into the dealer, and they put it in the bike at the 500 mile run-in oil change for me, obviously during the warranty period, without any hassle what so ever.
The bike also used "synthetic" RTS 5w-40 and Mobil-1 20w-50 with no problems. A lot of Victory owners also used syntheitc Mobil-1 15w-50 with excellent results.
I currently use synthetic 10w-40 or 15w-50, for a British bike. I could use 20w-50 synthetic, if I wanted.
Most American 50 weight motorcycle and atv specific oils are 20w-50. It is common.
Most manuals are close to a joke, anyway. I use it as a guideline only. Read enough of them, and you have an idea, what I am talking about.
Do you think the dealer, is going do a analysis on the oil? Not all dealers are created equal. I am lucky to have a reasonable one.
I would use a synthetic 40 or 50 weight, according to the weather, or keep using what works for you. Change the oil at the recommended oci, or do an oil analysis, too be sure.