If we called it a 100 mile hilly time trial that allows drafting
...it wouldn't be a time trial, because the whole point of a TT is that you aren't allowed to draft!
I don't think anyone is suggesting that people cannot get a sense of accomplishment from successfully completing the physical challenge of a sportive, and I don't see a relative scale of "worthiness" by which these events can be compared. The point is that road races, time trials and sportives are different types of event. You can't really discuss them in a sensible way if you don't understand and acknowledge the very specific differences in the way they are organised, the rules they operate under, and the way people participate in them.
[Are the] guys doing the Bealach Na Ba in under 4 hours...still sub-Cat 4 standard riders?
Who knows? A lot of people riding the Bealach are BC licence holders. A lot of people are not. Does it matter? Licence categories are just a way of classifying riders to make it easier to organise different tiers of road racing, so novices don't gatecrash elite events, and successful riders don't spend their time pot-hunting against beginners.
Sportives are potentially very good for road racing (and even TTs) in this country, because some participants, new to cycling, and initially attracted by the better marketing and publicity associated with sportives, will also find their way into club cycling and road racing.
Horses for courses, but understand the differences.