Google recognizes my iPhone as my iPad?

Yesterday I was trying to enable Google timeline on my iPhone 11 Pro, which requires location service.

But I didn't manage to make it work because I found something weird.

I have an iPhone 11 Pro and an iPad Pro 2018. And usually, when I log into my main Google account on both devices, I'm supposed to see two different devices in my Google account.

But Google always recognizes my iPhone as my iPad. No matter what order I logged in and what network I'm using, it is always shown as an iPad, not two separate devices. It's like my iPhone and iPad are recognized as one device

Here is a screenshot of my main account:

However, If I use an alt account, it can distinguish the devices and everything works fine. see below:

I've talked to google support and they couldn't figure it out either. Does anyone know how Google identifies Apple devices? Or is there any solution?