Hi, thanks for your reply.
These tabs are in a default tab group.
Force syncing seems to make the problem worse. I have 50 open tabs on my iPhone. Before force syncing, Desktop showed 6 synced tabs on that iPhone, as you can see in the screenshot below:

After the force sync, it now shows one synced tab. I'd put in another ticket about tabs suspending despite low-power mode being disabled. I think this issue is at least partially a result of that problem.
https://orionfeedback.org/d/11949-tabs-suspending-even-with-low-power-mode-disabled
But not completely, since even after following your instructions, my iPhone shows 23 synced tabs on my laptop, despite the fact that my laptop only has 21 open tabs. Additionally, a few tabs that my iPhone shows as being open on my laptop were closed hours ago (before I performed the force sync and reset instructions above), and a few tabs that were opened on my laptop before the force sync and reset are not showing in the sync list at all on my iPhone.