Airdrop, iPhone only receives when on wifi
tldr: iphone only receives airdrops when on wifi. can send regardless.
iPhone 12 and iPad Pro 4th gen, both are my devices on my icloud.
Both devices with active wifi connections to the same access point, AirDrop behaves as expected. Both devices can see each other in AirDrop. Files transfer between both.
Both devices disconnected from wifi (forgotten) but with radio enabled, both devices can see each other in AirDrop. iPhone can transfer files to iPad. iPad can not transfer to iPhone, "waiting..."
iPhone connected to wifi, iPad remains disconnected. iPad can now transfer to iPhone.
iPhone and iPad again disconnected from wifi. iPad can not transfer to iPhone, "waiting..."
iPhone disconnected from wifi, iPad connected to wifi. iPad can not transfer to iPhone. iPhone can transfer to iPad.
After connecting iPhone to wifi, iPhone receives missed transfers.
So it seems my iPhone can only receive transfers from my iPad when the iPhone is on the wifi network whether or not the iPad is also. I don't have any other devices to test with. I have tried cycling the radios and rebooting with no effect. The only thing so far that works is connecting the iPhone to wifi.
I understand in general how AirDrop works but am a new apple user. Something missing?