How does one define a specialist scheme - a ministry that offers a different scale?

So for example, MFA is a specialised scheme - then i think they use the FSO scale?

My question is are MOE Teacher’s (GEO) a specialist scheme also? What about Mindef (DXO), or some special functions in MHA that does not follow the MX scale?

It seems like specialised scheme pay more than the regular MX?