Yes, it's true. Unlike
scooter/RV/etc. rentals, Disney's FW prohibits offsite golf cart delivery/transactions from taking place onsite.
One company we were booked with a few years ago was iffy about renting to us due to rumors that others were threatened with trespassing or had received lifetime banning. They ended up cancelling our rental a month in advance.
Kenny's Tee Time will meet offsite and allow guests 1 hour to use their company truck/trailer to transport carts onsite themselves. In this case, you will need to take a taxi to meet them offsite.
Another method we discovered Tee Time uses is - if another guest is checking out or close to checking out, TT will arrange to have you pick up the cart directly from that guest's site, although I highly doubt that's allowed since it's still an onsite delivery transfer, except the guests are the ones doing it.
For example, TT asked if we would give up our cart a full day early at 8 am to another guest to avoid offsite transfer. We agreed to do so, but never received compensation for it. So Tee Time got double paid on a cart for one night.
Anyway, TT rental fee at $35 per night is almost half the cost of Disney at $62.84, but understand how they operate should you choose to go this route...