> I will try this on Linux later.

Confirmed. My results on Debian sarge are:
args[0] = linux
args[1] = fb
org.firebirdsql.jdbc.FBDriver
jdbc:firebirdsql:127.0.0.1/3050:/home/rrokytskyy/test.gdb
time1 = 1774 time2 = 190 time3 = 19094
time1 = 1797 time2 = 145 time3 = 19165


I will try to find out the reason. This should be somehow related to
networking, because this is specific to local connections only.

Thanks,
Roman Rokytskyy