Booting the kernel with "acpi=noirq" or "pci=noirq" disables ACPI's interrupt configuration code. If the system has no IOAPIC, or if it has an IOAPIC but has no MPS tables, then it will run in PIC mode. In PIC mode, the ACPI SCI should still function properly. But if the system has an IOAPIC and MPS, then it is at the mercy of MPS if the ACPI interrupt is going to work or not. ACPI will continue to request_irq() on the FADT.SCI_INT. However, this IRQ# may be incorrect for IOAPIC mode, or its polarity/trigger may be incorrect -- and the ACPI code that processes the MADT interrupt source override to customize this IRQ for IOAPIC mode does not correct it. In this case, the ACPI SCI may or may not work, depending on if the MPS tables happen to set up the interrupt in the way that the ACPI hardwar expects it to be set up.
acpi=noirq and pci=noacpi are workarounds for BIOS or Linux ACPI interrupt configuration bugs. Rather than complicate the code for the benefit of the workarounds, the focus should be on fixing the root cause issues that require these workarounds in the first place. So I'm closing this bug as WILL_NOT_FIX. Note, if your system requires these workarounds and you really want ACPI interrupts, then you can add "noapic" to run in PIC mode and the SCI should work that way.