My experience has been "it depends"

I have added my partner to my reservation at other hotels and had him check in without an issue, but we did have an issue at one hotel. No big deal as I arrived about 1/2 an hour later, he just had to wait in the lobby. I have not tried it when I was not coming and I have also called the hotel in advance to warn them that he would arrive before me. The final bill was also generally charged to my credit card.