The house rule limits the amount of "answers" you can process mentally in a given round/turn without some for of augmentation. The 2 means you could mentally process 2 full/deep answers in one round. Multiple Castings with Mastery 3 would produce 4 deep questions & answers in the same round and therefore overwhelm your mental capacity for the one round with information.
You could however solve this problem with other effects, as state in the House Rule.
You could use an effect to copy the information into a temporary memory locus for example. This is a Base 5 effect. So using this is an excellent way to give yourself temporary perfect recall to process things. You could also use something like Muto (to augment processing) or Rego (to control information flow into a locus, or to control mental focus) Mentem effects to directly boost your ability to process information and get modifications to your processing speed based on the effects you design. If you want to be able to rapidly do deep probes of multiple people without slowing down as it were, that requires investing in effects that augment capacity like this.