Schedule format with forward slash (/) not supported

[OffCorner]

Maybe I missed something, but it seems like I can't set a cron schedule that includes a forward slash like so:

*/10 * * * *

this should execute the cronjob at every 10th minute, so at :00, :10, :20, :30, :40 and :50.
I used the following command to update the crontask:

ee cron update 1 --schedule="*/10 * * * *"

and got the following error:
Error: Schedule format should be same as Linux cron or schedule helper syntax(Check help for this)

Incidentally, it is not possible to set multiple minutes either:

ee cron update 5 --schedule="0,10,20,30,40,50 * * * *"

The interesting part is when it comes to reading existing cronjobs. Running ee cron list website.com gives the following output:

+----+-------------+-------------------------------------+----------------+
| id | site_url    | command                             | schedule       |
+----+-------------+-------------------------------------+----------------+
| 5  | website.com | sh -c 'wp cron event run --due-now' | 0 5/10 * * * * |
+----+-------------+-------------------------------------+----------------+

The issue is that 0 5/10 * * * * itself is not a properly formatted cron schedule expression, at least when validated with a website called crontab.guru.
I suspect it should actually be 5/10 * * * *, but then again this cannot be set.
So changing an existing cron schedule makes it impossible to go back…