Yes that's fine if the company can determine what they want before setting dates, or asking for "estimates" (date commitments). Though the OP was talking about worse case of: date set, product/ux/etc continues (or starts) planning, eating well into deadline.
This might be a controversial take but if you have an actual deadline -- "product must cross the threshold of not shippable to shippable" as opposed to a cutoff date "product is at all times shippable but we need a date to say we're done refining" then agile is probably not the way to go.
I've always structured projects like this as waterfall to your MVP then switch to agile. You have to get your PMs to agree to an (externally) unchanging design and feature set until you have something working to talk about and then you can ask what they want next.
Even without a deadline I still try to follow this model but define the "MVP" as a "hello world" app but with functioning prod-ready infrastructure and ci/cd. So then I can go to the design meeting and say, "I have a blank canvas, what do you want on it?"