our architects love building the house before making the drawings. i imagine we will probably figure it out eventually when the feature set can be strictly defined.
(maybe you eventually want a bath tub and a toilet in each room? maybe not?)
(maybe you eventually want a bath tub and a toilet in each room? maybe not?)
This is different than commercial work where in addition to the original plans, you also get as-builts, which can be expected to be accurate, and are expected to be updated.
If you only want to document once, it makes sense to do it once the thing is built, rather than before, because there's a good chance the actual thing will be different than the plan. If you will update it, it might make sense to start documentation before the thing is built.
Of course, if you never get around to writing documentation, it never needs to be updated.
It really depends on the nature of the project, but UI design often requires a lot of "Paving the Bare Spots"[0]. It's really just too damn complex and counter-intuitive (or too intuitive) to catch in Requirements.
Software allows us to iterate this incredibly quickly. Hardware design also does it, but at a much slower pace, and a much greater cost.
[0] https://littlegreenviper.com/the-road-most-traveled-by/#pavi...