I think Covid-19 severity also depends on the person's immune system, rather than viral dose alone. For example, the article below offers a balanced view about this, citing a study finding similar viral loads in asymptomatic and symptomatic infected persons.

https://www.medpagetoday.com/infectiousdisease/covid19/88692

The point about re-inhaling viruses making one sicker is interesting and possible. But, honestly, I have not seen any concrete evidence of that.

Anyway, one problem I see about viral load studies is that they measure viral load from the upper respiratory tract via nasal or oral swabs. But the severity of Covid-19 depends on the virus and immune activities in the lower respiratory tract, i.e., the lungs.