I think what he is trying to say is:
The booking agencies (Agoda, Booking .com, Expedia etc.) charge varying rates to hotels. For 4 and 5 star they generally charge around 5% but for smaller hotels they charge anything up to 25%. For this reason booking directly with 3 star and lower hotels will normally get you a useful discount.
In addition in a smaller hotel will normally give you access to a manager who can authorise a discount, whereas the larger and more expensive hotels normally won't discount as you don't get access to a decision maker.
Small and medium hotels are increasingly disillusioned with the way they are treated by the major hotel booking agencies and are using airbnb and other such agencies who charge significantly lower rates. Savvy travelers use the major sites for information and planning, then book direct through the hotel's website or contact the hotel by phone