You're right, it could be the wind or birds flying by. . . my bet is on the modem, since the iPhone 7 / X (unlocked QC version) don't have these issues.
You really have that much faith in Intel? There's a reason that Apple dropped a boatload of cash into the Qualcomm deal, and that they are (rumored) to be putting ARM chips in the mac down the road. Intel has hit a wall in all kinds of areas.
Also, the design of the iPhone X / Xs is the same. If it were an antenna issue, those with the QC Modem on the iPhone X would have complained, yet it was only those with the Intel modem that noticed a difference in signal quality.