We were following WPF interface that only offers two versions of the constructor (1 or 4 values): https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/Windows/Thickness.cs,34
Anyway, we think it is safe to add that extension to the code so we'll do it for the next release. Although using it will mean code won't be compatible with WPF, just want to remark that.