DVC is very unlikely to go after someone who rents once, even for a large number of points, because DVC has no way of knowing whether such a use is a rental (that is, money was given to the owner) or a gift (owner put the reservation in someone else's name and no money changed hands). If it was a rental and the owner was paid, DVC has no way of knowing whether the amount was sufficient to result in a profit for the owner, or if the amount paid was less than the annual fees that the owner paid. Investigating someone for a single transaction will result in a lot of "false positives" in which the transaction is with a friend or family member (which is explicitly permitted as personal use, whether or not money is involved).I think that this conflates two separate but related concepts: 1) What constitutes a prohibited rental, and 2) How Disney can identify people engaged in prohibited rental activity.
A single non-personal-use rental is prohibited, even if you ever only do it once over the lifetime of your ownership. We can go back and forth for days over what constitutes personal use for the purposes of the various terms and conditions (and Disney has given us some new hints about how they intend to interpret those provisions), but the second that line is crossed, then Disney is entitled to cancel that reservation.
DVC is saying that "regularly or frequently" renting would be not be personal use. Regular and frequent bookings for other people could still be for personal use if they are not rentals, but such bookings can be noticed and monitored. When someone books a number of reservations for a number of different people, DVC can take a closer look at whether these are people for whom the owner has booked before. If these are all distinct people with no prior connection to the owner, DVC may start watching future transactions or contact the owner to remind them of the rules against commercial rentals or start blocking future (and possibly even current) reservations.