In CMA the designations of Siu & Dai are minor & major, primary & secondary if you like, not the literal small & big.
Yes, other CMAs often use
Siu and
Daai to name mother-son forms or complimentary subsystems.
Is there a
Daai idea, form or subsystem to your WC? If not, it doesn't really make sense to have minor without major, or primary without secondary,
Siu without
Daai.
Also, you said you don't even use the term
nim-tau (idea), and that it may have been changed to this by YM? But then you talk about the "little idea" in your system.
So, I'm a bit confused as to why you have an interpretation of it. Is this something you came up with yourself or has your system borrowed and reinterpreted the terminology from YM?
As an aside, the third character,
tau, is a suffix for nouns. It doesn't carry the literal meaning of "head" or figurative meaning of "first" in this case. As an adjective, it would need to come before the noun it's describing.
In
nim-tau (idea) and
lin-tau (training) it acts just as a suffix. So,
Siu-lin-tau, as you use would mean "little training (set)". It would make sense to have a
Siu with or without a
Daai if that is all it means, not so much if it means minor or primary without a
Daai.
For us, there is no
Daai because VT is just this one "little idea", a simple approach to fighting.