It’s a little different than that, some oscillators have a triangle core and others have a ramp core, from which other waveforms are derived, but that doesn’t make them smaller necessarily.
But it is true the amplitudes out of a 3340 are different for the different waveforms.
It is also true the perceived loudness depends on the wave shape as well as the amplitude. A sine wave sounds quieter than a square wave of the same height.
Rather than cutting volumes with trimpots on the outputs, a better approach is to add amplifiers on the outputs. That leaves you with larger amplitudes and lower impedance outputs. The Kassutronics VCO3340 for instance does that.
The MFOS VCO creates the triangle wave from the ramp in such a way as to keep the same ±5
V amplitude, the sine shaper has an amplifier as an integral part of it with a trimmer to set ±5 V, and the pulse wave is created as ±12 V and attenuated down to ±5 V.