Anything RF is deep wizarding lore, a world filled with wonders unexplainable to laypeople.
The effect is well known, and the reason why if you open up your average phone, there will always be a ton of shielding around components. All the high speed buses can and do create lots of side emissions... so in order to allow a phone to function with its extremely tiny bunch of antennae in direct proximity to the chips, all components get shielded from each other.
In desktops and even most laptops however, the high-speed (and thus high-frequency) chips and their clock traces are very far away from the wifi/bt antennae, so for a long time manufacturers could get away with not shielding anything, just taking care about ground planes, trace length and impedance matching and spacing. Nowadays, with buses getting ever faster and faster (to the point where analog design criteria take over priority), I think we'll start seeing shielding rather sooner than later, and we're already seeing CAMM modules getting implemented in devices for the same purpose.
Side note: that's also why you're not supposed to operate a computer's parts without a case at all or with a partially open cases. The case itself acts like a faraday cage.
If you have external antennas you can (or at least could) actually try this. Having the RAM just behind the antennas (by holding them in an open case) with a clear line of sight to the router produced significantly worse results than moving the antenna 30cm in either direction.
I can't remember which WiFi generation I was testing this with but I remember seeing something like a 40% reduction, worst case.
The effect is well known, and the reason why if you open up your average phone, there will always be a ton of shielding around components. All the high speed buses can and do create lots of side emissions... so in order to allow a phone to function with its extremely tiny bunch of antennae in direct proximity to the chips, all components get shielded from each other.
In desktops and even most laptops however, the high-speed (and thus high-frequency) chips and their clock traces are very far away from the wifi/bt antennae, so for a long time manufacturers could get away with not shielding anything, just taking care about ground planes, trace length and impedance matching and spacing. Nowadays, with buses getting ever faster and faster (to the point where analog design criteria take over priority), I think we'll start seeing shielding rather sooner than later, and we're already seeing CAMM modules getting implemented in devices for the same purpose.
Side note: that's also why you're not supposed to operate a computer's parts without a case at all or with a partially open cases. The case itself acts like a faraday cage.