I am a software engineering manager at a FAANG company. I own a software system critical to company operations internally that I proposed turning into a product. My org doesn't have Product Managers and I've never worked with them betore now, but now I am as they work up the plans for the product.
They've already set an aggressive timeline for product release (approximately 3 quarters) and they're putting forth these promises in the initial documentation that are kind of crazy for features that range from technically hard to probably impossible without asking me for input until I'm periodically reviewing mostly finished documents and raising concerns.
They've got some misunderstandings about the underlying technology, which is fine and expected, but they seem to be talking to external potential large customers then coming back to me with bizarre feature proposals to solve for problems that I don't think actually exist. I don't want to go into too much detail but a very large potential customer apparently expressed, based on what they think is a core technical limitation, that they wouldn't be able to adopt the product. PMs came back to me with a rube goldberg device proposal to essentially work around this fundamental problem with some real 4D chess, but I'm 98% that this problem is not a thing at all, as we regularly do the thing internally. I don't know whether the proposed company is missing something obvious or they are Jedi masters that know something I don't. So far I can't talk to the potential customer directly to understand the issue.
I've raised enough various corrections and context that they're asking me to jump in and write the docs "with them" but to do this I basically need to do it for them. Which I could, yes, but it's getting awkward, and I don't have the access to customers, sales data, and other research tools they've got. I don't mind, per se, jumping in and taking charge, but I'm having some role confusion on what my place is in this effort and I am worried that since I'm not experienced working with PMs, instead of being helpful, I'm just not understanding how this process is meant to go. Maybe wild claims of what the product will do based on vibes is just part of the early stages? I'd be fine letting this play out, and dreaming big is important, but then they've set this quite specific and near timeline based on nothing and it's unclear what resources I'll be given to accomplish these claims.
At what point do I move from reactively correcting issues one by one, and move to proactively taking over large parts of the process, or ringing alarm bells that something is not right? Obviously one answer is to talk this out with the PMs, but I'm looking for some context before I jump in. Thanks for any advice.