To be fair, I never said it can be done entirely by post, but questioned whether an appointment to attend the court was the only way or if you could send the SD to the court. The reply was that you'd still need to attend the court at some point, but that wasn't the issue.
I said that surely it's quicker to send the SD to the court by post, the result being enforcement paused on receipt rather than wait for an appointment to swear the SD at court, an appointment that could be days or a week away, or with the Covid19 situation even longer.
Advice that you must 'make an appointment' also doesn't consider whether the sentencing court is nearby or not.
For me if it was a choice of sending a sworn SD by 1st class signed for which would see enforcement paused within 48 hours, or making an appointment to attend the court at who knows when with enforcement remaining live until you attend the appointment, then the postal option wins every time.