Yes and no, but let me make sure you understand what happens. The projector is native 16:9 as most are now. Whatever the light output you have is based on that. When you watch scope, you only use the middle of the panel obviously. And that means only that portion of the pixels, and the light output...roughly 25% less than with the full panel. But, when you zoom, you are taking the image and making it larger, which ultimately decreases the foot-lamberts off the screen, even though the light from the projector is not less. So ultimately that yields an even larger perceived drop.
Whether it is an issue depends on all your specs (room, size, etc...) and personal preference.