I agree, they shouldn't be in the quiet period by now. Only thing I can think of is anything related to financial department (BO, JV, funding or even Uplisting) or maybe they really have nothing to discuss. If they don't announce ASM this week or next week you know something is cooking.
Or perhaps NWBO would simply refuse to announce an application for regulatory approval as this is in keeping with their general mentality. This is a company that often chooses to withhold information which while not material, is something a reasonable person would know shareholders would find useful and interesting and which the company can choose to share or not share at their discretion.
I am not saying you are wrong but just that with NWBO especially, there is every chance they could file and just not tell us just because.
That is a simpler and more plausible explanation than a buyout.