About the readonly attribute of setting items

Hi, this is my first post.
I can't enable the readonly attribute for an item in settings.xml.
Is there something I'm missing?

It works as expected in the App Settings Editor, but Garmin Connect and Garmin Express don't allow the boolean type readonly to work and toggle on/off.

The version is up to date.
Garmin Connect(4.31.2.1)
Garmin Express(7.0.0.0.0/Mac)

Best regards.

<settings>
  <setting propertyKey="@Properties.Theme" title="@Strings.Theme">
    <settingConfig type="list" required="true">
      <listEntry value="0">@Strings.Original</listEntry>
      <listEntry value="1">@Strings.Dark</listEntry>
      <listEntry value="2">@Strings.Light</listEntry>
      <listEntry value="3">@Strings.Red</listEntry>
      <listEntry value="4">@Strings.Green</listEntry>
      <listEntry value="5">@Strings.Blue</listEntry>
      <listEntry value="6">@Strings.Yellow</listEntry>
      <listEntry value="7">@Strings.Black</listEntry>
    </settingConfig>
  </setting>
  <setting propertyKey="@Properties.Emboss" title="@Strings.Emboss">
    <settingConfig type="boolean" required="true" />
  </setting>
  <setting propertyKey="@Properties.Battery" title="@Strings.Battery">
    <settingConfig type="boolean" required="true" />
  </setting>
  <setting propertyKey="@Properties.Connect" title="@Strings.Connect">
    <settingConfig type="boolean" required="true" />
  </setting>
  <setting propertyKey="@Properties.Heartrate" title="@Strings.HeartrateDisabled">
    <settingConfig type="boolean" readonly="true" />
  </setting>
</settings>