You can try convincing me of your flat earth theory but without any references (hyperlinks) it just sounds very made up to me 
This problem weirdly doesn’t exist. 
Nothing expensive just cheap off the shelf wifi stuff. Rock solid without any quriks on a round earth 
And what I really wonder - why are there so many - even very extensive - troubleshooting guides for zigbee but not for wifi?
Might be that zigbee uses the same shared ISM radio bands like WIFI but with the downside of being low power/bandwidth and subsequently “loosing” any air time battle against every cheap ordinary wifi gear out there if the environment would be really congested? 
Again: Never ever had (over 5 years running esphome, today over 100 nodes and cheap $10 used wifi AP’s for the last decade) experienced any degradation of service - on the other hand delayed/prevented/limited function of zigbee devices is a very big topic in this forum
Last thread with zigbee in the title from 30 minutes ago 