What you’re hoping to do should be possible without a problem. I just tested the structure in one of our portals and it works as you described (I changed the URLS for the screenshot): redirecting the home to a new page and retaining the query string.
My settings (in some of my attempts) were the same as yours, but I updated my current redirect to match your settings. I found that it now works, but not every time I load the original page. I have no idea why. Doing more tests seem to indicate that the redirect is occuring more often, so hopefully that means it will eventually worj 100% of the time, as expected.
Are the results still intermittent? I have tested from a couple of browsers and incognito windows on my side and it’s currently working consistently.
Are there other similar redirects in place as this current has a position of 1,000,000. You can try making that number much smaller to see if it is more consistent. If so, there’s some other conflict in your redirect listings.