abrupt speed changes and TCP

[Michael Thomas]

So it occurs to me in the rollout of 5G just walking down the street you 
might shift back and forth between high speed 5G bands and 4G because of 
uneven deployment and all sorts of other reasons. It sounds like this 
could vary block by block practically.

I assume TCP just views this as congestion? But with all of the 
congestion avoidance algorithms and the rapidly fluctuating bandwidth, 
wouldn't that result in the sender essentially adapting to the least 
common denominator (eg 4G)? The same goes with latency, I suppose for 
real time apps.

Mike