To me it comes down to impact velocities. Strangely, I'd be more apt to recommend a 150Gr with a .308Win or an '06 than with a .300WSM. Impact velocities over 3000fps can be difficult to predict with lighter constructed slugs. The higher the impact velocity, the more important bullet construction becomes. Like I mentioned in my earlier post, Most bullet manufacturers rate their bonded slugs to impact velocities of 3200fps and many of the lighter constructed slugs like the CT Ballistic Silvertip that the OP shoots can be quite unstable at impact velocities over 3000fps. I'd hate to have an elk step out inside 100yds and hesitate to shoot because the bullet is flying too fast to insure proper terminal performance. To me, with a 150gr BST the range envelope for that rifle would start at approx 150yds where that slug drops back below 3000fps and extend out to how ever far the OP is comfortable shooting, not to exceed 500yds That is why, for me, there is hesitation about a 150gr BST with the .300WSM.
Hope that can provide some insight as to why some people said no. Velocity is a good thing, but you can have too much for slugs to expand properly.
Just my .02...