The paper is showing about a 100x reduction in infectivity from exposure to saliva collected “0 minutes” after drinking tea. That’s a very small effect. Compare to, say, penicillin, which will kill viruses in the levels present in your blood and tissue hours after taking a small pill.
Or, for a different comparison, I don’t know of anyone testing a handgun against COVID (sorry, xkcd), but pool water and presumably chlorinated tap water reduces infectivity by at least 1000x in 30 seconds:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8480993/
Maybe one could use these compounds in tea as a basis to try to develop a useful antiviral drug. But numbers like this don’t make it look like the pandemic could have been averted by telling everyone to drink four cups of tea a day or to continuously gargle chlorinated tap water.
(Seriously, I doubt there were evil authorities out there trying to get people not to drink lots of tea so they could drum or support for mask mandates or quantitative easing or whatever other measures seem horrible. This whole concept seems utterly absurd. And at least opening a window or using a MERV 13 or N95 or better seem like more justifiable public health measures than distributing free bottles of iced tea!)