Is room size considered when they design speakers?

Yeah, good one, a dealer speaks

Like selling a +200hp car for 130km/hr speed limit? 
Many mini monitors are too expensive and many towers with multiple drivers are too economical.
Also some manufacturers claim use for their products in limited or larger space.
G

Maybe you could consider asking the specific manufacturer or respective dealer  the question. When I was looking to purchase Daedalus Audio speakers one of the things I discussed with Lou was my room size/layout and he went through which models would be better suited to my room. Likewise, when I purchased JM Reynaud speakers Bob at Amherest Audio and I also had that conversation going through JMR’s lineup.

Great questions!  I too can’t figure out if big speakers work better in big rooms or small ones.  Manufacturers of speakers give no guidance as to what speaker works best where.

2 companies that come to mind are OHM and Canton, both give guidance as to what speaker works best in what space.

And another great question is why does a 7 series BMW cost more than a 3 series?

Ohm speakers do exactly that. Website lists the proper size for a particular size room. Larger room needs larger speakers. Larger speakers cost more. Very simple and easy to choose.  The design scales up and all sizes deliver the same sound set up properly.    Nobody else does this that I know of.  Makes it easy to pick the right speaker for your room.