You can look at any given F2P game cynically in that way -- that the only reason to launch any F2P match (or game, really) would be to break-even or profit. But if they'd only started NGS without bringing over the original PSO2 Meseta in any way, there'd be a lot of content NA players could be missing out on, which includes items you may buy in PSO2 and carry around to NGS. (Which is the reason even using Tweaker and playing the JP servers would not be the same, since you could not carry any of the over to NA servers.) Plus, since they chose original PSO2 will stand alongside NGS, they were going to have to port both over anyway, so better to get it done in stages.
(I strongly suspect that NGS is not going to launch with a"complete game's" value of articles, but will be released progressively with time. This is most likely why they are upgrading the original PSO2 and keeping both side-by-side -- since folks will run out of things to do should they only play NGS.
By enabling units/weapons out of buy meseta pso2 to be brought into NGS, it'll give people a reason to keep on playing PSO2 in order to encourage their advancement in NGS, and I suspect they will incentivize people doing this in the first year or two until NGS is more fleshed out and fully-featured. In a way such as the relationship between PSO2es and PSO2 in Japan.)
This should be like it's own post. Im coming to the conclusion too. At first I was cynical but now that I know the larger vision more, it's all making sense. I am really glad we do not need to wait for 8 decades and are getting it all at one time.