In Freddie Patek's 3-HR game in Fenway Park, he collected two off journeyman Dick Drago. Drago would actually have an adequate season, slightly above replacement value for a long reliever. But he was susceptible to the long ball, giving up 17 in 131 ?. His HR/9 rating is 1.15 and HR/9+ is 71. On this occasion, he also served up a HR to Rick Miller, representing half of Miller's total for the season. Perhaps Drago was unready, having been brought in during the second inning.
Patek's third HR of the game came off Jack Billingham, a one-time good pitcher suffering a calamitous final season, including 9 HRs in 31 ? innings. His HR/9 is 1.99 and His HR/9+ is 41. Unsurprisingly, these pitchers have no WIS performance histories.
It would not be unrealistic for one of these pitchers to give up a HR to another low-power guy like Charlie Hollocher, especially making allowance for the dead-ball era. It would not be unrealistic for a good pitcher mildly susceptible to HRs, fatigued and pitching in a small park, to give up a HR to Hollocher.
Under the circumstances described, though, you should read the response from administration as, "Please don't ask too many questions about our modeling."