While I'm not an expert, I'm pretty sure the problem is that manufacturing the -70 freezers is more akin to the N95 mask manufacturing problem than the ventilator problem.
Even normal fridges require special chemicals and a vacuum process to manufacture. I'm pretty sure a -70 system is exponentially more complicated and has a lot more safety issues. If you can't get the right chemicals, if you aren't properly set up to handle the toxicity or environmental issues, or if you don't have the right tech to deal with the vacuum process, it may not be a simple matter of converting production lines. That's where a lot of the talk about Dipping Dots comes it; they're one of the few companies with the right production base to even consider repurposing.