As to who is a five-tool player, it all depends what you mean. Does the player have to be outstanding in all five areas, or is a little above average OK? If the latter, then sure I’d put Adam Jones in that category.
Being a five-tool player may be overrated, though. Frank Robinson didn’t have an above average arm. Does anyone think Jones was the better player? Maybe we need another category, excellent players with no glaring weakness. Frank fits that category.
Starters going 9 innings more and actually completing games, allow for more BIP.
Even your team's fireman/closer was expecting to pitch into the 3rd inning.
Lefty specialists for one batter was a concept not invented yet,
The days before the DH, even the AL played small ball, and bunting the running over, or the hit and run, sacrifice an out for movement of the runner.
I wonder if or how much those numbers are influenced by the fact that in Brooks' era there were a little over half as many strikeouts as in Manny's, and that far fewer players in the 1950s-70s tried to hit every ball in the air.
Back of the napkin, I get 500 balls in play per team per season gone because of Ks, and another 150 from the GO/AO differences just from 1990-2019. So if there were even more ground outs in 1966 the Orioles probably saw at least 300-400 more infield BIP than the 2019 Orioles.