No, and here is why.
No, iPhone or Android phone hotspot/tethered to a tablet or iPad will provide the iPad/tablet with a GPS position.
Timeero works by “asking” the iPad/tablet location services for an accurate position. If the iPad/tablet decides the position information it is receiving is not enough, it will not save the GPS position to the Timeero app.
When a GPS position is being provided by a GPS inside the iPad/tablet, this signal will usually be of high quality and rapidly updated, meaning Timeero will consider it as valid position information. But, when you are tethering to a phone, the position information is sent sporadically in between all the other tasks happening on your device (like sharing the internet). The data signal is very poor and will be insufficient to provide a continuous position to the iPad/tablet.
It's important to note that using a 'hotspot' GPS signal from your phone will give 'intermittent' position updates (the position will update momentarily and the airplane 'present position' will appear on the map). At face value, this can make people think tethering for a position signal is going to work. It won't though, and the position will drop back out in a few moments, especially if you start moving. Tethered position data is simply not accurate enough to be useable by Timeero.
If you have a wifi only iPad, to get a GPS position you will need a dedicated external GPS for iPad.