Quick search of some of the more notable goal scorers in history, best I got was Bossy @ 24% in 79, Lemieux 24% in 93, Gretzky at 26.7% in 84, Robitaille 24% in 1990. There could be others that high but I only checked a handful of names.
(full seasons or close to it only; Bure had 29% one year but he played only 11 games)
They didn't start calculating SH% until 1960, so one would have do the requisite math to see if Richard ever hit that high.
There’s been 5 guys with at least 40 goals who’ve been over 28%, all in the 80s
Charlie Simmer in ‘81: 56 goals, 32.8%
Craig Simpson in ‘88: 56 goals, 31.6%
Wendell Young in ‘85: 40 goals, 30.5%
Rob Brown in ‘89: 49 goals, 29.0%
Jari Kurri in ‘86: 68 goals, 28.8%
Though Kuzmenko shot 27.3% two years ago in his 39 goal season.