Plausible, yes. If the data exists, it should be made public. The article still mostly just makes a hypothesis and makes the argument that this is something that should be seriously investigated, not that the author has determined without a doubt that this is a lab leak.

Sure - but what are the chances that whichever hospitals did the sequencing even know they're in possession of the intermediate data? The OPs' method of "just asking questions" is really bad science and feels a whole lot like the God of the Gaps argument style that Creationists are so fond of using.

I'm not sure the best way to judge the quality of a scientific argument is whether it 'feels like good science.'

While the author is obviously only scratching the surface in an article targetted at non-scientists, the several PhDs he cites make decent arguments that are based on a little more than feelings. It would probably be more in line with the ideal of 'good science' to actually investigate the possibilities presented than dismiss them from emotional associations.

It is a worrying trend that the way science feels is increasingly more important than the actual evidence (or lack thereof). One could even describe the current attitude towards science outside of scientitific institutions as religious.