I have no idea what is meant by this. In my opinion, the information is wrong.
The Google Pixel 6a has only one slot, and that is for the nano-SIM. You can still use an E-SIM as a second SIM, provided your provider allows it.
This is also what it says here in the Google support article:
https://support.google.com/pixelphone...
However, up to 10 E-SIM profiles can be stored. So you can load 10 E-SIMs onto the mobile phone, but only have one active. And you can then be reached via this and the physical SIM card, and can make calls, text or surf.
With the 6a, it is also not possible to expand the memory with a microSD card.