Assuming I’m understanding you correctly …
Not so. (With the “right” image; one with very saturated colours), the result of CM can be observed in both the image itself and its related histogram - by toggling Soft Proofing ON/OFF even with CR de-activated (and including with SP’s “Protect Saturated Colors” setting = zero).
I’m not sure if your wording (in italics) was intended to imply that something different occurs when the WCS setting is Classic/Legacy(?) … but, if so then that’s not so either; the result of CM being applied can be observed for both/either WCS setting.