With the following configuration I receive Sflow from both aggregated interfaces:
(HPE Comware Software, Version 7.1.045, Release 2432P01)
sflow agent ip 1.2.3.4
sflow collector 1 vpn-instance legacy ip 10.10.10.1 port 9995 description collector.test.nl
interface Ten-GigabitEthernet1/4/8
port link-mode bridge
port link-type trunk
undo port trunk permit vlan 1
port trunk permit vlan 2 to 4000
sflow flow collector 1
sflow sampling-rate 10000
port link-aggregation group 330
interface Ten-GigabitEthernet2/4/8
port link-mode bridge
port link-type trunk
undo port trunk permit vlan 1
port trunk permit vlan 2 to 4000
sflow flow collector 1
sflow sampling-rate 10000
port link-aggregation group 330