It's a sure thing
It is of course entirely possible that all of the above reasoning is wrong, that Helion truly believes it can do 10 impossible things before breakfast and Microsoft agrees.
My bet is MS doesn't really care. It gets some positive publicity, a tax writedown and can probably sue Helion if (hah!) it doesn't deliver. But maybe Helion can deliver something. I agree that the timescales look unrealistic, especially approvals. Downside to He3, other than price and availability is dealing with all those pesky fast neutrons. But maybe Helions figured out a way to create a neutron speed-trap and can capture that energy in a way that doesn't lead to the neutron absorbers becoming ever more radioactive. The paperwork to demonstrate this is safe and sustainable is probably going to take >5yrs.
One of the amusing projects facing this problem is Cornwall's Eden Project. They decided to do some fraccing for geothermal power. Cornwall, being granite and fairly radioactive gives them the challenge that their working fluid and stuff like heat exchangers will be irradiated as the system operates, which leads to the 'green' project needing a bunch of radioactive waste licences and compliance costs.