It doesn't feel like a 1911 safety, nor is it shaped like a 1911 safety. It doesn't work the same way like a 1911 safety (the XD series is not a hammer fired SAO with a thumb safety).
I feel like someone put a grip safety on a Glock because SA makes 1911s and they thought it was cool. To me it's stupid and unnecessary.
I also find myself holding XD guns higher and tighter than I want, putting the web of my thumb at risk, to reliably engage the GS. There's a reason nearly all of my 1911s have BGS.