As @finity says, the person integration is designed to be able to use multiple “trackers” per person to provide a more accurate estimate as to where the person is. This can help since often individual trackers aren’t all that accurate, or can sometimes take a while to update, etc.
FWIW, at least IMHO, the person integration doesn’t always do a very good job of it. I created a “composite” tracker long before the person integration existed. It addresses some of the shortcomings in the person integration’s algorithms. It’s not necessary perfect either, but I believe it does a better job in general. In any case, if you’re interested, see Composite Device Tracker Platform. You can certainly use it in conjunction with the person integration. I.e., use the mobile app and ASUSWRT trackers with the composite, and then use the composite tracker with the person integration.