That's not correct, nor is it logical.
If there were a chargeback issue with a processor, or with a merchant account, reducing the number of transactions coming through the gate would actually make the chargeback situation worse.
For instance if someone gets 1000 sales and 3 months later there are 100 chargebacks from those sales, that would be a 10% cb ratio in the month the chargebacks came in - NOT referred back to the month the charges were made.
So if you then decided to scrub so hard that the number of transactions the next month was only 500, you would still have the same chargebacks coming in from 3 months prior -- when there was a problem under your theory of scrub -- and with the same 100 chargebacks you would have a 20% ratio, or double the ratio.
HOWEVER, if you doubled the transaction volume to 2000 transactions, that same 100 chargebacks would end up being a 5% ratio, a drop by half.
Neither 5, 10 nor 20% is allowed, I chose the numbers to make the math easy for the example. Chargebacks are allowed in percentages under 1 or 2, depending on the region, and getting more volume is the name of the game.
So this theory of scrubbing is yet again proven false.
Who knows why some days suck and some days are great. There is no real logic for it, and the law of averages isn't formulated on one days worth of numbers.