Can iPhone tethering (hotspot) give the iPad a GPS position?
No, tethering will not provide the iPad with a GPS position.
OzRunways works by “asking” the iPad for an accurate position. If the iPad deems the position inaccurate enough, it will not pass the position to the OzRunways app. Using a 'tethered' GPS signal from your phone will give 'intermittent' position updates, but these are not useable by OzRunways (you may see your 'position' pop up momentarily though).
If you have a wifi only iPad, to get a GPS position you will need a dedicated external GPS for iPad.