Noticed when reviewing MDL-73683.
This issue has a couple of things to consider:

1. For a restricted activity (e.g. available after some date in the future), teachers see BOTH a lock icon next to the section name and a lock icon in the availability information present within the first part of the section. The locks mean different things. The first one (next to the section name) is the result of the 'available' check. That is, whether the section is available to the current user. The latter is just a representation of the fact that the section has some restriction applied to it.

What this issue should consider is whether the first lock icon (next to section) offers any value to the teacher, given 'available' isn't something that really applies to them.

2. For certain restricted activities (e.g. a group restriction, or a date restriction set up with a past date), the teacher sees no lock next to the section name. They only see the availability information in the first part of the section. This may be confusing to teachers, and is also difficult to explain to them because the meaning of the first lock (next to section name) is hard to relate to their role (as explained in 1 above).

Examples of the above can be seen below - there were taken using the editing teacher role.

This one shows the lock being displayed both next to the section name and in the availability information.

and this one highlights the issue in point 2 above; the lack of that lock next to the section name for teachers in certain circumstances.