Quoting the source which contacted TAP directly:
“If you have not started grind for Steven, it is high time to do it: In 0514 update he will receive the following buff: • Expert Loader (75% to reload time when the shell type is switched, while ordinary skill give 50%) • Expert Marksman (+3 deg/s to the traverse speed of guns with a caliber of up to 139 mm. +1 deg/s to the traverse speed of guns with a caliber above 139 mm, while ordinary skill gives +2.5 and +0.7 )”