[BC66] Why do both QCGDEFCONT and CGDCONT ask for an APN?

I am a little confused about the commands AT+QCGDEFCONT and AT+CGDCONT in the BC66 commands manual. I’ve read the description, but don’t quite understand what the difference is. All I really see is that both commands ask for an APN. Is the same APN required for both commands? And if so, what is the point of that? Why would have a user have to input the same APN twice?
Specifically I am confused because some tutorials tell me to use the QCGDEFCONT command, and others say I should use the CGDCONT command.

The description of the APN parameter for both commands is exactly the same:

String type. A logical name that is used to select the GGSN or the external packet data
network. The maximum configurable APN length is 99 bytes. If the value is null or
omitted, then the subscription value will be requested.

If anyone has any accessible reading material that explains what is going on here, it would be much appreciated!

+QCGDEFCONT is a Quectel proprietary command.

+CGDCONT is an industry-standard 3GPP command, implemented on all makes and models of cellular modem.

+QCGDEFCONT accepts an username and password. If these are required, they need to be handled elsewhere if the 3GPP command is used to set the APN

3GPP AT commands can be found in 3GPP 27.007 (3GPP 27.005 for SMS commands).

AT+QCGDEFCONT is used to configure the IP protocol type and APN parameters of the PDN. (This parameter can be left blank by default. However, if a private network is used, apn_name,username, and password need to be configured.)
AT+CGDCONT is mainly used to configure the PDP. PDP is related to your data service. Normally, relevant configuration is not required