Why is foreach not recommended in unity

First look at the article https://www.zhihu.com/question/30334270 there is a picture

This explains the process of having a boxing after each foreach loop, and what is boxing? (See here: http://www.cnblogs.com/xiaoshi/archive/2008/05/28/1208902.html) The simple thing is to convert a value type to a reference type. The second line here is the boxing process. The third line is the unboxing process, which means that each time you use foreach, you apply a reference memory (40Bytes, a reference to a list) to the heap at the end, and the reference memory is recycled at gccollect time. The recycling process will be jammed. So unity does not use foreach because it generates garbage memory that causes the lag

Why is foreach not recommended in unity