This article is really misleading. There is nothing explicit whatsoever with this in Starfield. You never even kiss. You just get the regular loading screen after sleeping except that your romantic partner appears to have woken up next to you, and you get a slightly better version of the Well Rested xp buff. It’s not a “huge XP boost” over the normal Well Rested buff
I did a private wedding with just my wife, photographer, beautiful venue for $600