Have you attached the reversal set to your ledger?

Yes you are right, adjustment entries are reversed in the next period.

One reason where you would reverse journals in the same period would
be where you have entered the journals by mistake and you wish to
"undo" them. You would not want such reversals to happen automatically
though. You would do that on need basis.

In the video I am not sure if I have reversed the journal in the same period
for a purpose or whether I simply picked just one period. The focus
of the video was to show to how reversals work. If you have any questions,
I can re-watch the video for you to find out more. Yes you are right, adjustment
reversals are reversed in the next period, not in the current period.