Skills with 0 pt with default values are not taken into account for attack levels

[Ayutac]

For example, if some attack uses Innate Attack (Projectile) and this is only at level 0 (but still in the skill list), the attack isn't given a level.

[Ayutac]

See also page 173 of Characters. It says defaulting doesn't give benefits of skill, e.g. combat bonuses. But if you can aim a little bit, you can aim a little bit, right? I guess the GURPS developers themselves have to be asked.

[Raszul]

There is a related issue.

The default "natural" attacks (Punch, Kick, Kich w/ Boot) are only based on the "base" unarmed combat skills. They ignore the Combat Arts and Combat Sports versions.
If my understanding of the rules & skill descriptions is correct then the tool should treat "Brawling", "Combat Art (Brawling)" and "Combat Sport (Brawling)" as being basically identical.

It doesn't.

In fact it ignores the Combat Art and Combat Sport skills completely (as does almost all equipment).