I have a DB view that list all orgs and a WS which extract them.
I have 2 Webservices roles on the client.

#1 : is IsUseUserOrgAccess = 'Y' and user has access to all organizations (AD_User_OrgAccess)
#2 : is IsAccessAllOrg = 'Y'

=> #1 : RowCount = 0 (whatever the OrgID is)
=> #2 : RowCount = 3

If I set RoleType = '' for role #1, I'm able to log in webui and see all organizations in the window based on the DB view.

Conclusion : WS doesn't use the content of AD_User_OrgAccess table when querying for data.
Is confirmed by logs :
17:01:31.533===========> MRole.getClientWhere: No Access Org records [4255]
17:01:31.540===========> MRole.getOrgWhere: No Access Org records [4255]