copy & paste from that link:

" This encryption happens as it is written to disk, without the customer having to take any action. Google encrypts data with distinct encryption keys, even if they belong to the same customer. Data is encrypted using 128-bit or stronger Advanced Encryption Standard (AES).

Google encrypts core G Suite data while it is “in transit” as well, whether it is traveling over the Internet between the customer and Google, or moving within Google as it shifts from one data center to another. We encrypt this data between Google and our customers using HTTPS with forward secrecy. "

The truth nobody knows but it seems that they encrypt with their own keys so that means they can open the data and read it.