As long as my state and all other states(to my knowledge), insurance companies and Harley Davidson consider a TG a motorcycle = it is a motorcycle. People can call it whatever they want. Some people call ships, boats and tomatoes, vegetables. Completely wrong on both counts, just shows their level of education.
One could play with semantics forever, even Harley calls the Triglide and the Freewheeler a trike. When you go to their site both the TG and Free are under the heading "Trike", the P&A catalog will make statements about fitment with the caption "Except Trike". When I had my 2010 TG it was considered a Trike by my insurance company Allstate. When I was putting insurance on it the agent was having a hard time finding it until I told them look for FLHTCUTG, she then said there it is, a trike. My 2012 Hannigan wing is insured as a bike with accessory coverage equivalent to the cost of the trike kit, that is how they handle a triked 2 wheeler.
IMO a bike which grows a 3rd wheel is a trike.