On 8.10.44 the submarine HMS VIVID sunk NW of Chios island, the concrete ship ACHILLES and what are generally mentioned as two tugs named PAUL and HORST.

Actually HORST was not a tug but one of a series of iron riverine vessels built by Ewald Benninghaus at Koln in the mid/late thirties. Most of them had a grt of 210-212 and some of them were taken in 1942/43 to the Black Sea and later in 1944 to the Aegean.
HORST was actually built in 1938.
I believe that PAUL (212 GRT) was a similar vessel, can anyone confirm?

Also, HMS SPORTSMAN sunk on 31.3.44 the GRAUER ORT generally recorded as a "sailing ship". She was also of 212 GRT. Maybe she was also a member of the same class of riverine vessels?