A resolved task, that is not visible to me and thus show up as "Restricted task", is, when added as blocking task (probably also for blocked ones) to another, not shown struck out in in task details.
Example: on T85909 there are two blocking tasks, T 86555 and a restricted task. Below in the comments/log there is "RobH closed blocking task Restricted Task as "Resolved".". The restricted task is still shown as normal and not struck out like other visible tasks are.
(I'm assuming the task was not reopened in the meantime, but I can't check that)

See also: T90833: Private tasks should have a placeholder on the workboard