Yeah I use the Small Business series extensively, and for the SG300/350/500/550 their hostname only ever reports as either a factory default switchblaaah
or a hostname set in the administrative interface.
You might want to check on the router whether the MAC address of the listed device actually matches the Cisco MAC and look it up on a HWADDRESS type site too. The router might be reporting old information some other client that historically had either the same lease or else the same factory default IP and is mixing them up.
The only reason I would think to see an unexpected hostname is if sold pre-owned (or opened and returned) without being factory reset.
prlzx on iDNET: FTTC (VDSL) at ~40Mbps / 10Mbps
with IP4/6 (no v6? - not true Internet)
Edited by prlzx (Mon 24-Feb-20 00:43:03)