If you’re not latency sensitive, such as queue to queue lambdas, then go for it.
Pretty sketchy marketing in my opinion.
I think you would expect them to at least use swap for density and always keep one extra instance running and ready to serve requests. It's not like people generate functions on the fly, so it shouldn't even cost anything extra. Swap will help with unnecessary things kept in memory.
2. The last company I worked for isolated functions to vms on a customer level. That way, if someone hacked their way past the function container, they would then still have to hack their way past the VM container to access another customers data which is what you would have to do anyways on the public VM offering.
For example if your sign up process is lambda you did you got your cost benefit analysis wrong on anything other than a prototype or mvp, but if your 'change your profile photo', something that maybe happens a handful of times across a month on average per user at best, and you implemented that as your lambda to reduce load and delay scaling needs on your core infrastructure then that feels like you did it right.
Business: OK great that sounds like what we want.
1 Month Later:
Business: We were really successful with hundreds of requests a minute, but for some reason the delay came back!
Tech: Oh...warming up doesn't scale. Scratches head and walks away.
And because it's a "Cloud" service, we pay for what we use, so if there's no workload for the functions to service, there's no cost. We just pay for the time the tiny little container is active.
Business: Ok, that sounds like it can save us money, and you seem confident in the technology, let's go with that.
1 Month Later:
Business: Why do all these actions take so much longer to complete? They used to load instantly with a "Done" message, now they're measurably delayed to respond.
Tech: Well, you see the containers that run our functions stop running once they've finished their work and it looks like theres nothing more for them to do, so when new work comes in theres a delay while the container starts.
Business: You mean like how my Dell takes 5 minutes to boot up?
Tech: Well, kind of, but its much quicker than that obviously, and it's not a whole operating system, it's just some processes in a process namespace...
Business: <visibly zoning out>
Tech: Ok, well tell you what we can solve this, we can setup something to periodically ping the system so the containers running our functions don't ever get de-activated, and that way they'll be ready to service requests immediately, all the time.
Business: OK great that sounds like what we want.
1 Month Later:
Finance: Why did our bill for "functions" suddenly spike in the last month, compared to when we started using it?
Tech: Well you see now we have to keep the function containers running 24x7 so they're quick to respond, because $Business complained they're too slow to start up from inactive state.
Tech Onlookers: ..... <blink>.... Wat... Why... Why would you do that?
(Edited to add:)
Tech Entrepreneur: I can outsource that process of keeping your function containers active for you, for just $1/container/month!