[bogantech]

Maybe they're using DDR3? Looking at a micron DDR3 datasheet there's no maximum for active-to-precharge

:edit: no, I should have read the paper - they tested with DDR4. Strange

[jhallenworld]

I found the "ACTIVATE-to-PRECHARGE command period" in a Micron DDR3 datasheet, same value: 9 x tREFI

https://www.mouser.com/datasheet/2/671/4Gb_DDR3L-1283964.pdf

Page 78, speed bin tables.

Refresh basically is an activate/precharge sequence, so keeping a row open long is the same as denying refresh to that bank.