Does AlphaCommerceHub require the `SuccessURL` be served over HTTPS?

The «AlphaHPP» → «Paypage Request Reference» → «Request a Paypage Session» table does not mention it:

Parameter Name Type Mandatory Description
SuccessURL Alpha O Allows the merchant to define a different URL the response should be sent to from the default configured URL, for example for mobile support

No. It would be good practice but https is not required for SuccessURL