There's nothing special about the transformer in SMPS other than it's size which is due to the high frequency.

The other problem they create, then, is high frequency noise which must be filtered out. Some cheaper adapters just dump the noise back into the mains and cause problems for _other_ devices.

Come to think of it there's a decent chance it's a /different/ adapter somewhere on his system that's causing the problem and not the size or capacity of the products native adapter.