Theme / CSS inheritance when using a theme per view in Lovelace

I have two themes configured. theme_a and theme_b. Theme A is a light theme that I use as the default for HA. Theme B is a dark theme used for a specific view only. In Lovelace it is configured like so:

  - title: Dark Section
    icon: mdi:tablet
    theme: theme_b
    path: tablet

I am struggling with inheritance and contamination of styles between the two themes. In theme_a for example, I have defined: paper-item-icon-active-color as a yellow colour #FDD835. I have then chosen a different colour in theme_b: paper-item-icon-active-color: '#3182b7' but I am still seeing items in yellow on the Dark Section view.

It is worth noting that I am using the theme refresh service after every change: frontend.reload_themes but it doesn’t fix the issue.

I wondered if there is some trick I am missing when using a theme for a specific view? … or is it simply not possible for a single view to control some CSS properties?