i usually use this chart from the Athletic as a reference
obviously none of these are going to be perfect or even necessarily good approximations, but if we assume the Canucks 2nd will be around 38 (2.2 GSVA), my "replacing the 2nd" calc is essentially one 4th between 104-108 (0.8), one between 109-114 (0.7) and another between 115-122 (0.6) - adding up to 2.1 GSVA.
And that's just on average - but if they really think for example, that the top end of the second round of this draft is weak but the fourth has more depth than usual - by all means, there is a theoretical play here. But I don't think that's how they're approaching it.