It's so appalling that a paid content could be that bad. For me the first benchmark that was doing nothing in both cases is as shocking as the second.
But the thing I wanted to highlight is that the blog author is a real authority on structs vs classes at a very very low level. His series on structs performance are must read for any .NET dev who cares about performance at low level. E.g. when to use readonly structs or when to use a mutable one to avoid excessive copying. That kind of things. https://devblogs.microsoft.com/premier-developer/author/sete...
He has published two analyzers on NuGet and both are must have. One is focused on the struct usage ErrorProne.NET.Structs and, for example, highlights cases of defensive copies and could suggest when to make a struct readonly.
https://devblogs.microsoft.com/premier-developer/avoiding-st...