Yes, under the Handling Time option, you have to ship your orders on time for eBay to compensate buyers.
But you also have to upload tracking information to remain in the Guaranteed Delivery program. For both options, there are ongoing performance standards which are in line with Top Rated Seller requirements:
A minimum of 97% on-time handling on Guaranteed Delivery transactions.
A minimum of 95% on-time tracking upload on Guaranteed Delivery transactions.
If sellers fall below those standards, they might be removed from the program.
You will see that these standards are only for Guaranteed Delivery transactions. If you have items which take longer to ship or you can’t send using an approved service, make sure that is accurately reflected in the listings. Then they will not qualify for the program and won’t affect your metrics under it.
Note that you don’t have to be a Top Rated Seller to participate in Guaranteed Delivery. Top Rated Seller has additional performance requirements. The only connection is that the two performance metrics above are set at the same levels for both programs.
eBay provides a Guaranteed Delivery dashboard under the Seller Hub performance tab to help sellers track their performance.