This is one of those topics that there will never be a consensus in my opinion.
During my 45+ years of biking, I have heard the following definitions to indicate someone who is bicycle touring. Bike tourist, cyclotourist, bike touring, fully supported touring, supported touring, self-supported touring, self-contained touring, fully loaded touring, light touring, sport touring, bike packer, bikepacking, sojourner, biker, crazy guy on a bike, MTB packing, credit card touring, expedition touring, off-road touring, e-touring (pretty new to term to me), etc. This is probably not the entire list and a lot of the terms are misleading as they, to me, describe the style and/or bike setup.
To me, "bike packing" is a relatively new term. Again, I have been touring for 45+ years and that term is maybe 10 years old as a mainstream term.
The problem is as you say semantics. I personally would not qualify "sport touring" as someone with 45# of gear. Maybe 25# (max) or less. More along the lines of "credit card touring". For instance, I go on a multi-month tours with no more than 35# (without water and "average" food). Only time I get over 45# is if I have to carry a ton of food and/or water.
However, others would love it if their gear weight was only 45#.
Then there are the sub-categories. What is the difference between motorcycle sport touring and adventure touring? I thought motorcycle adventure touring as more off-road touring regardless of weight. What would a off-road bicyclist be who has 50# of gear be doing? Say his riding buddy had only 40# of gear. Are they doing different kinds of touring even though they are on the same route?
I am not trying to argue per se but just show the discussion of trying to define what defines a "touring bicyclist" is pretty fluid.
I personally prefer the term "cyclotourist" to indicate a touring bicyclist regardless of the type of bike or road condition of touring he or she is doing. I prefer the terms "paved" or "off pavement" touring to describe the road surface touring of a particular route as I have seen traditional touring setups on the great divide and have seen bikepacking setups on the TransAm but to described the TransAm as off pavement would be misleading. From there we can get more specialized but then that is where the waters get muddy.
Of course, everyone is entitled to their own opinions. I wish we could come to a consensus but I will not hold my breath.
Tailwinds, John