While a T-shirt has the same purpose in S M or L, a table isn't the same if it's lower smaller than 50cm or longer than 1.5m, or lower than 60cm or higher than 70cm. In a standard shop you'd call that a night stand, or a coffee table, or a kids' table or living room's low table etc.
If you think of it as shopping for an environment (same as half of the in-shop experience: they'll show you full rooms where you can see products fit together) it makes sense. Somewhat.
https://www.ikea.com/jp/en/cat/hemnes-bedroom-series-58619/
And the other Hemnes lines include book stands, dish cabinets, TV stands.
I totally agree IKEA doesn't give a damn about series and collection consistency.
[1]: https://www.ikea.com/us/en/cat/chests-of-drawers-10451/?filt...
Please look at it quickly and try understanding what elements are available.
Or, say, Platsa having half of the pieces called Småstad, because they kinda would also fit in kid's room. Or trying to find codenames for doors/facades/drawers of Metod or Pax.
The list even isn't sorted and looks like a SELECT without order from a database.
It is really odd they don't have a (sub) category page for each of the series.
e.g. this dresser is available in many sizes but you wouldn't know from the product page: https://www.ikea.com/us/en/p/storklinta-3-drawer-chest-white...
At best you can then search for "STORKLINTA" but the result list has the other sizes mixed with all sorts of other products such as beds: https://www.ikea.com/us/en/search/?q=STORKLINTA