Ian,
Sybille was on station until 25 February 1901 so, in theory, most of the men on board should have received the SA01 clasp. Looking at the roll for HMS Sybille, very few people received the SA01 clasp. Of the 272 entitlements, 187 were for a no clasp medal, 80 for the single clasp CC and the remaining 5 received CC and either SA01 (4) or CC and SA02 (1).
Looking at the other ships that were in South Africa into 1901, they seem to be in a similar position with few issues of SA01. It is possible that only if the ship returned for the so called 'extended period' did they gain entitlement to date clasps.
It would seem the entitlement to the clasps was applied differently by the Navy and Army?
Regards
David