Clearly, hitting a cache would be the better outcome. The technique suggested here could only apply to unavoidably cold reads, some kind of table that's massive and randomly accessed. Assume it exists, for whatever reason. To answer your question, refresh avoidance is an advertised benefit of hardware mirroring. Current IBM techno-advertising that you can Google yourself says this:
"IBM z17 implements an enhanced redundant array of independent memory (RAIM) design with the following features: ... Staggered memory refresh: Uses RAIM to mask memory refresh latency."
I can google, thanks. My point is that nobody is buying mainframes with redundant memory to avoid refresh stalls. It’s a mostly irrelevant freebie on hardware you bought for fault tolerance.