I have the same problem - esxi host webclient can't browse nfs 4.1 data storages. Version 3 of nfs data storage work fine. If I use the virtual center I can browse the v4.1 nfs storages too.
ESXi Host WebClient
Version 1.8.0
Build 4516221
ESXi
Version 6.5.0
Build 4887370
Regards
Jochen