Agreed, it's a judgment call. The OE brass screen is pretty effective and cleanable. If you're running less than 5 gallons of fuel through your bike, per year, there's unlikely to be much dirt...certainly nowhere enough to clog anything, unless you get a criminally-bad batch of fuel.
IMHO, the external fuel filters (and Tygon fuel hose) are more applicable to modified bikes that see some mileage. Being able to see fuel flow, or lack thereof, on-the-fly can come in handy...like when "reserve" is reached. Plus, modded bikes are likely to run single-inlet carbs & remote petocks, with a single outlet. More room and a single filter is easier to deal with than twin filters on a stocker.
FWIW, I also wipe down the inside of the tank, at season's end. The white tank liner makes the dirt impossible to miss. That's not directly applicable to many members. However, some may benefit from my experience. I generally run through 10-20 gallons per season. Seems like the tank collects more crap than it did the previous year.
As for using the bowl drain as a diagnostic tool, when lack of fuel delivery is suspected...standard operating procedure. You just have to be off the bike.
BTW, draining the entire system via the bowl drain, at least once a year, is a good idea...easy to do, as well. Drain the fuel into a large funnel, lined with a coffee filter and you'll see how much sediment was inside the bowl, if any. You should be draining the system dry as winter storage prep anyway, also a good time to clean the stock fuel screen too.