As far as I can tell, the longtime Second Guest Stays Free Honors benefit has been dropped, as of the 2023 terms for the program. This is not a surprise, as Hilton stopped touting the benefit over the last year or two. Also, in the US, single travelers have been booking double occupancy to get double F&B credit, so perhaps Hilton is looking at charging for the 2nd occupant to help recoup F&B credits.
Not IME over many 2023 stays, with the exception of a few HGIs which always seem to be outliers.