The carriers are just going to push a software update to change the indicator for LTE-A to 5G, I think AT&T already did that...
So for this part, you do not have to worry about 5G being short range or easily blocked. Compared to LTE you will still get benefits like flexible numerology (ie. lower latency) and full duplex (ie. increased bandwidth).
The name 5G is more of a marketing term rather than an accurate technical description, just like the term "retina display". Different vendors can market the same technology very differently. For example, HSPA was marketed as 3.5G, 3G+, Turbo 3G, 3.7G, 3.9G and even 4G. It did not help that HSPA evolved a bit during its lifetime. I would not be surprised if operators arbitrary decide to call whatever they are using 5G.
If 90 percent of the phones in a cell can be hoisted up to the 80Ghz spectrum, then the remaining devices can each have a much larger share of the 800Mhz/1.8Ghz spectrum.
As the leaves blow about in the wind, devices will dynamically shift bands every few milliseconds.