Extreme Management Center does try to get information from Securestacks only through SNMP and there is much less of information we do gather compare to EXOS.
From EXOS we gather information through SNMP and http/https and CLI = check if all methods are available & working.
Do you have stack or EXOS or single unit? more ports => more time. more vlans => more time.
Regards
Zdeněk Pala