401k- can actively trade upto 25% of assets

Your article in ActiveTrader, "The Proof is in the RETURN", states, "Furthermore, those with a Mini 401(k) can actively
trade up to 25 percent of the plan’s assets, and all
gains are tax-free until the trader retires. Mini 401(k)
traders can also borrow money from the plan." Where does this restriction of 25% arise from? I checked with Fidelity, and they are not aware of any such restrictions.
thanks.