Build on top of v1.8.3-alpha.81.
The user pinned the remaining front-card blur to the side cards backdrop-filter, and they were right. Each side cards ::after used backdrop-filter blur to give the perspective-depth-of-field cue. That filter creates a new stacking context on every back card, and on chromium-class browsers the side-card stacking context bleeds visually into the FRONT cards rendering layer, the front-card content (text + chart curves) rasterises at fractional resolution alongside the back-card filter.
The depth cue is now plain opacity: side cards at 0.88, back cards at 0.70. No GPU filter, no compositor layer, no side effect on the front card. Loses the gradient-blur on the side cards, gains a sharp front card on every layout.