If export doesn't show settings, then that's definitely a bug. On my RB951G export displays relevant settings:
[user@RB951G] /interface ethernet> export
# jul/12/2019 12:50:53 by RouterOS 6.45.1
# software id = QCG5-PSG8
#
# model = 951G-2HnD
# serial number = 642E05BB727B
/interface ethernet
set [ find default-name=ether1 ] name=ether1-router
set [ find default-name=ether2 ] name=ether2-BOX
set [ find default-name=ether3 ] name=ether3-AV
set [ find default-name=ether4 ] name=ether4-TV
/interface ethernet switch
set 0 mirror-source=ether1-router
/interface ethernet switch port
set 0 vlan-mode=secure
set 1 default-vlan-id=40 vlan-header=always-strip vlan-mode=secure
set 2 default-vlan-id=42 vlan-header=always-strip vlan-mode=secure
set 3 default-vlan-id=42 vlan-header=always-strip vlan-mode=secure
set 4 default-vlan-id=42 vlan-header=always-strip vlan-mode=secure
set 5 vlan-header=add-if-missing vlan-mode=fallback
/interface ethernet switch vlan
add independent-learning=yes ports=\
switch1-cpu,ether1-router,ether3-AV,ether4-TV,ether5 switch=switch1 \
vlan-id=42
add independent-learning=yes ports=switch1-cpu,ether1-router switch=switch1 \
vlan-id=2
add independent-learning=yes ports=ether1-router,ether2-BOX switch=switch1 \
vlan-id=3999
add independent-learning=yes ports=switch1-cpu,ether1-router switch=switch1 \
vlan-id=41
add independent-learning=yes ports=switch1-cpu,ether1-router,ether2-BOX \
switch=switch1 vlan-id=40