interfaces interface-name vlan-tagging

Can anyone explain the purpose of the vlan-tagging statement under interfaces interface-name ? The documentation says it exists "to enable the reception and transmission of 802.1Q VLAN-tagged frames on the interface"

1. How is this any different from simply configuring set interfaces family ethernet-switching interface-name port-mode trunk?

2. The documentation states "On EX Series switches except for EX4300 and EX9200 switches, the vlan-tagging and family ethernet-switching statements cannot be configured on the same interface." This suggests that it can be configured together on the EX4300 and EX9200 -- why would I want to do this and what purpose does it serve?

https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/vlan-tagging-edit-interfaces.html

Thanks,

--Paul