JOSM - Comparisons in MapCSS: do they only work with constants?

way[start_year > setting("start_year_to_display")] { /* does NOT work */
    opacity: 0.1;
}
way[start_year > 2021] { /* works */
    opacity: 0.1;
}
way[setting("start_year_to_display") < 1950] { /* works */
    opacity: 0.1;
}

It seems, that you can only use constant expressions on the right hand side of a comparison. Is that true? And are there any workarounds?

PS: Originally I thought you can’t use a setting() from type double in a comparision, but that is obviously not the cause of my problem.