Freedom initially gives you 6040 split yes, but subnetworks are free to use what rev share they may like to offer, they are not dependent on the 60/40.
so you got 55/45. If you did $100 on YT, you will get $55, the remaining $45 are split between that subnetwork and freedom in a % agreed on their contract.
If initially agreed a different rev share and then sneakly put you another one at the time you signed it and didn't notice it than that is all different story. But you should always double check the number in the contract.
but bottom line, networks and subnetworks will and can only take the % of the agreed rev share. Subnetworks will not and can never take extra from your cut. All they can take is according the rev share signed and agreed.
There is no financial loss for the youtuber that signs a subnetwork, normally there is a gain because subnetworks tend to offer better rev share than the parent network,