The context we need is how and why the players in question have compiled that particular combination of average and strike rate; not context about this hypothetical match as such.
It's extremely unlikely that someone who averages 55+ and strikes at 75 over a long period has a lot of those runs coming in at 4 down with 15 overs to go. His record in that situation is probably
a lot different. It's not that people think having someone come in and score 34* (45) on average is going to be more useful than having score 30 (25) instead; it's that
a) #6 batsmen are confronted with more than just this situation
b) someone with an average of 55 and a strike rate of 75 would very likely do something different in that situation.
If we lift the curtain and admit we're still talking about Bevan and Maxwell, I'd consider taking a high strike rate/mediocre average player like Maxwell in this specific situation (assuming batting first). But Bevan's overall career numbers aren't really the reason. When Bevan batted second he always scored at close to the optimal rate of what he was chasing, and given Australia had a really good attack, this meant he often didn't score very quickly in the second innings -- he just didn't need to. In first innings when he was setting a total, he averaged 52 and struck at 80 instead, which I think is a more accurate way to look at Bevan than as a 55/75 player. It's also worth noting that during Bevan's career, the
global strike rate for all players was 72.19. During Maxwell's
it's been 83.32. A strike rate of 80 during Bevan's career was roughly worth a strike rate of 92 during Maxwell's, which again isn't real near what Maxwell produces, but we've definitely moved away from the misleading blanket career number.
A player's strike rate is not just formed by his natural scoring ability, but the context of the situations he faces. If you give him a situation different from the one he's compiled most of the runs in his average and strike rate in, he will very likely produce a different average and strike rate in that new context.