You are right, in so far that they don't suddenly change the specification of every vehicle being manufactured from a single, fixed point in time. They assemble a set of sub-systems to meet or exceed a least common denominator spec. It makes it simple for them to build and for us to buy their cars.There is no model year Tesla.
However, they have, co-incidentally or not, introduced a raft of changes for the 2022 calendar year and updated the published specification to reflect changes to the underlying sub-systems. Have a poke about in the html source of the 'Design Your Model 3' page and you'll see comments like "New SR+ with BTF1 Battery GF03 SOP 10/1/2021" or "New LR AWD Trim w / BT43 GF03 SOP 11/8/2021" and "New Perf Trim w / BT43 GF03 SOP 1/1/2022". New is better.
In all models, new means a new battery sub-system (BTF1 or BT43) and the published spec (range) was updated for the new batteries before the start of the calendar year. The battery is probably the single most important sub-system of an EV. Rightly or wrongly I associate the 2022 model year with the battery and would feel short-changed to get last year's technology, even if it met or exceeded the new spec.
I couldn't care less about the number of loudspeakers, USB ports or whether the rear glass is laminated or not. These are the kind of inconsequential spec variations that occur throughout the quarter and year.