My Cannondale Topstone came with a 105 FD and I put a GRX crank on it and it worked fine. I suspect you can go the other way around. It might not be ideal for the derailleur but I bet it would work.

There's no such thing as larger than 48/31 combination in GRX rings from Shimano. Though I can't say there isn't some non-GRX rings that could work from Shimano or someone else. Probably go with the 105 cranks set.

By the way, when people say the GRX 600 group set is like Shimano 105, they mean in general quality, cost and value. Or where it fits in the gravel group set range versus where 105 sits in the road group sets. Not that they are mechanically interchangeable in all aspects. But they are pretty close, since GRX is essentially a road group set.

I'm not going to argue about what the OP wants and why. But, pretty much no one is spinning out on flat ground, riding solo with a 46/11 other than in a sprint. Even a rather low cadence of 80 RPM would be a speed of about 28 MPH. I'd have to hold over 400 W to go that fast on the flat. Of course an extremely strong tailwind could do it.

A much more modest, but still respectable solo speed for an average Joe might be say 20 MPH, and with a 46-11 combination the cadence would be around 57 RPM which is unusually low. So, I too find this all very curious.

But regardless of the conditions one is spinning out on, there's a reason to have larger rings for road riding and I think going with a 105 crank set is probably the cleanest and should work fine with the GRX FD. But if not a Shimano FD-R7000 front derailleur is about $30. And it is compatible with the GRX shifter, so not a big risk.

As mentioned the GRX crank set chain line is 47 mm and the 105 is 43.5 mm. So 3.5 mm closer to the frame (~1/8"). It's probably fine, but worth looking to make sure there is no issue with chain clearance on the frame or rear tire. Makes me think to be sure to note where the rings are relative to the frame and make sure if they move in 3.5 mm there no issue with the frame. Again, I don't think there will be, but it's worth checking.

The FD will have to be raised about 8 mm to go from the 46 to 50T ring. Probably not an issue, but again something to check.