The wings are thought to be an anti-browse defence against elephants / mammoths, etc. - chew the twigs, and (apparently!) the bark wings break up into an intensely bitter and astringent mouth-puckering dry powder. Just what I've read, I've not tried it myself!!
The mystery looks to be the version 'Compactus' dominant in North American horticulture and also perhaps what makes up most of the nuisance infestations in eastern American woodlands. This does not have the same level of wing development as the typical species.
Interesting. My pics posted on 28th Sept showing red leaves and berries are from my plant in the garden. Bought as Euonymus alatus compactus...I have often wondered why it doesn't have the winged stems. Now that mystery has been resolved. Thank you Ron.
Just had a good look at your 1st images...see below I can see the seeds hidden amongst in the leaves.