“Walls are thinner.”
Some RVs have aluminum siding. Does that stop radio waves? I realize there are windows.
It can, depending on many factors. Weak signals, higher frequencies are more impacted by walls to begin with. Weather. Funny enough, vegetation can absorb higher frequencies like VHF (30-300 MHz), UHF (300-3000 MHz or 3 GHz) and Super High Frequency (SHF is 3 GHz - 300GHz). WiFi operates on 2.4 (UHF) and 5.0 GHz (SHF).