Another 26 Nosler question.

I see MidwayUSA offering a RCBS #38 shell holder for the 26 Nosler and some of the short mags. One reviewer said his short mags would fit the std. #4 mag shell holder. He questioned wasting his money on the # 38.

What's the difference between the #4 and #38 shell holders? Gotta be a reason for the #38.

DF