If i use a GCD skill and directly afterwards trigger a instant skill, the instant skill will automatically queue up and reliably trigger a second later.

If i put the same instant skill inside a macro via /ac "my skill" and do the same chain the macro fails to queue up and nothing happens. If inside a macro it seem the same skill now needs to-be triggered at least 1.5s after any GCD skill and no queuing happens?

I tried to safe precious controller crossbar space, by having multiple instant skills inside a macro, but the macro does trigger so unreliably because of this difference that its rather problematic to use.

So why does the instant skill outside a macro queue up and trigger reliably, but doing the same inside a single line macro works differently? This is not explained anywhere in the macro system or guides?