so while Firecracker was designed for thing running just a few seconds there are many places running it with jobs running way longer then that
the problem is if you want to make it work with long running general purpose images you don't control you have to put a ton of work into making it work nicely on all levels of you infrastructure and code ... which is costly ... which a startup competing on a online dev environment compared to e.g. a vm hosting service probably shouldn't wast time on
So AFIK the decision in the article make sense the reasons but listed for the decision are oversimplified to a point you could say they aren't quite right. Idk. why, could be anything from the engineer believing that to them avoiding issues with some shareholder/project lead which is obsessed with "we need to do Firecracker because competition does so too".