Last login determines presence device?

I did an investigation this morning.

I have an iPad7 and an iPhone12.
I went thru all my apps and deleted my iPhone from them.
I then deleted my iPhone as a device.
I logged off the iPad and logged off from the iPhone.
Then I deleted the HE app from my iPhone and my iPad.
I booted the iPhone and the iPad.

I downloaded the HE app from the App Store on the two devices and logged on HE from my iPhone. It created the device of iPhone12.
I sent a push thru HE to my phone. It worked.

I then logged into the HE app on my iPad. It asked me if I wanted to create a new device or use the existing device. I chose existing.
I went to the device (iPhone12) on the iPad and sent a push.
The push went to the iPad instead of the iPhone!

Whatever device you log into last, determines the push and possibly/probably the presence sensor.

Could this be the problem all along with presence?

Most of us have several "computers" we log into to do changes to HE.

Why? Your iPad and iPhone are two separate/distinct devices. If you want to use them both (or either one alone) for presence, you should create separate devices on the hub for them.

Only if one chooses not to create separate Hubitat devices for separate devices running the mobile app

Note - this has no bearing on accessing the hub interface via a regular browser.