Be aware that v13 probably works in .NET 9, so when you multitarget based on the .NET version, you might end up installing your v14 version of your package in v13, if someone was to run Umbraco 13 in .NET 9. When v9 came, .NET 6 was released shortly after, and there was some who chose to run Umbraco 9 on .NET 6.