Seemed to be a bit of a dig at Keystone for not being an NHRA track now or then...but was NHRA from the late 1970's up through the late 1990's/early 2000's (?) for what it's worth. I think they joined IHRA around 2001-2002, and now WDRA. I believe they were running under NAAR in '72, which was started by Walt Mentzer. Walt was the original founder of the AHRA. Useless info of the day.
I grew up North of Pittsburgh, no one ever really talked about Keystone being "fast", so I can't help but to believe Ivo had the perfect storm that night to run the 5.97.