[Findecanor]

Actually, no keyboard exhibits "ghost keys" — phantom key presses. The difference between methods of "anti-ghost"ing is whether ghost keys are avoided completely (e.g. using diodes), avoided for some key combinations (e.g. "gaming optimised matrix") or just suppressed (detected and blocked).

99.9% of mechanical keyboards made in the last decade avoid ghost keys by using diodes, yes, primarily because they have been intended for gaming.

However, diodes are not at all universal in mechanical office keyboards, even if they use discrete switches and a PCB. If you'd look at vintage mechanical keyboards, you'll find that while many have them, many don't. Cherry even still makes some older models with Cherry MX switches and 2-key rollover.