Ground planes do matter on receive. On strong signals using a roof gutter won't really matter, but on weak signals, the antenna will be noticeably directional.
That's the theory and theory is a fine thing. But practice dictates otherwise, after many years in the 'industry' I can say with certainty that it will make very little to no difference. If you believe otherwise then so be it. I dare say the OP will no doubt post his results.
I'll order it, it is advertised as not needed a ground plane, but I assume I can always put the antenna on the tin roof of our patio if a grounded area is needed.
Also, this is not a perfect environment, we do not have spherical cows or perfect vacuums, if there is a little bit of bias in the directionality of my omnidirectional antenna, I'm okay with it. I live in the suburbs, have a budget, and am not relying on this radio for any life-critical use.
I'm happy with minor imperfections.