But to clarify that also means it will not be deleted if for example;
Played in Season 2-3, hasn't played since
BUT owns some skins they bought in S3
therefore will not be deleted correct?
Yes, you won't be deleted. You owned skins in S2-3 which means you either purchased them, were gifted them, got them through a promotion (hello, Championship Riven, which is legacy) or probably played enough to earn them through ranked play.