All this talk about how a particular MIDI C does not equal a particular Hz C aside…
Your intuition is probably correct. Compare a synth to an 88 note piano… if you have to sacrifice notes, you’ll choose to lose more from the top octaves than from the bottom, so that’s how the patches will be tuned. The mid and bass get a lot more use than the extreme highs.
I would add: the disconnect between MIDI and Hz can be used to your advantage. eg: when designing a bass sound, you can tune the oscillators down so that the range you will want to use is accessible around ‘middle C’ on the keyboard, rather than having to transpose the keyboard every time you want to use the sound. (Which doesn’t sound like a big deal, but it’s easy to miss a good sound when auditioning patches because you’re hitting notes that are outside its intended range.)