Hi Tony,
It is not normal. The real speed should be lower than the theoretical one, but it shouldn't be such low.
But I tried to flash 32KB data into KL17, it costs 9.7s on Windows, 14.5s on Linux.
My Linux system is Ubuntu 14.10 32bits under Virtual Box.
I'm not sure if it is your OS's issue. Could you please re-try on other PCs?
Best Regards,
Yitao