The apparent lack of care from Apple regarding this quite fundamental issue with a key iOS feature is disgusting.
The last exchange I had with one of their support representatives, I was told:
”With IOS 13, there have been some instances when you are on a FaceTime call via wifi, that the wifi icon goes away but it is still using the wifi connection.”
I am astonished they are peddling such utter rubbish. When the icon switches from Wi-Fi to 4G/LTE, the connection is immediately impaired which is no coincidence.
I guess our only hope is iOS 14 however the chances may be slim as they seemingly have no clue what is going on here.