I don't think he means that masterclan heroes must be used for this. They should be masterclan to generate additional command point.
The alliegence ability for masterclan is :
Each time a friendly MASTERCLAN model uses a
command ability, roll a dice. On a 5+ you receive 1
extra command point.
So when Thanquol use his command ability, you spend a CP (which can generate another one a 5+) and then, each other masterclan heroes that use his free command ability given by Thanquol can generate another CP on a 5+.
Clever use of a not so clever writing. The masterclan ability should read :
"Each time a friendly MASTERCMAST spend a command point, roll a dice. On a 5+ you receive 1
extra command point."
Cause right now, when Teclis cast total eclipse, when you spend 2 command points for a command ability, you can only generate back one. Can can't roll for 2 CO spent.
Highly specific but well.