The biggest problem with carbon offsets is that they're not pinned to a particular time of day.

If you buy a 1 GWh block of wind/solar energy for a month, you're not doing anything to supply clean energy when it's dark and the wind isn't blowing.

"24/7 carbon free" means increasing the time resolution from 1 month to 1 hour, and funding projects that deliver clean energy when you're actually using it. This includes stuff like batteries, nuclear, and geothermal.