I've not had that happen - the things I've done recently we've booked we've had to specify a Lead Traveller (or some similar grandiose name), which is just whichever of us is organising/paying for it.
If they've not specified your husband as 'leader' in some way - just put him first of four with no distinction other than being first - then I'd just check it isn't something straightforwardly programmatic. For example, if you were called Beatrice, Zebadiah, Alfred and Maximilian, you might get re-ordered to A, B, M and Z. Or date of birth order. Just a random thought from someone who spends a lot of time ordering data
I thought of that. I am first alphabetically, and I am the oldest of the group.
I'm chatting to them online. they have confirmed that I am the lead passenger, and are telling me alternately that a) they changed the order; b) it doesn't matter and c) they didn't change the order.