the WiFi specifications are backward compatible and go thru exhaustive testing to be as close to perfect as possible.
Design implementations are another story. How operating Systems influence connection speeds is less than perfect. For example a laptop path to its home router may bounce off many walls before getting to destination. If these signals appear as out of phase "echos" at microwave lengths at the same amplitude, they cancel and that dead spot may only be a few mm every 10cm. Meanwhile the user is oblivious to this condition and thinks he/she is close enough to get a good signal. So the operating system driver tells the Wifi adapter to drop the connection speed and try again. THis may affect the path and dropout enough to be above the noise threshold and work. A better solution is notify user that the signal is marginal or "strong signal with strong reflection noise" and move to a different direction and hold the mobile device steady.
Education is key in the above example and a scholar may read about Rician fading but educating the user how to make Wifi compatible is not hard as it generally works universally when the signal is strong. When it is weak, then sources of interference including its own signal with walls and cordless telephones on the same channel are the most common issues.