I think Airbus and Boeing FMCs work in very similar ways in this particular circumstance, mainly because they have to. They will attempt to stay on a pre-computed path until environmental conditions make it impossible within certain parameters and either call for drag or add power. The exact implementations are probably different but the logic appears the same.
I find the most vulnerable phase is a high CI descent from somewhere close to the tropopause when you’ve been cruising at optimum altitude. A constant angle often does not work well when the speed margins are at their slimmest and wind/temperature can change abruptly with a small change in level.