David has said this. But in essence encrypted packets are similar if they are https (one form) or another application encrypted packet (NNTP encrypted say). They have the packet header and encrypted payload. https when using the better https is a header and encrypted payload.
The real need is not in that the individual packets are in the same form as https but for patterns when intense DPI is being used. DPI for encrypted https only works if the encryption does not encrypt the whole payload. Remember DPI on encrypted packets is greatly hampered since the DPI cannot read port# or domain name or anything else in the payload unless the browser is using the lesser encryption. SAFE is fully encrypted so DPI cannot distinguish it from fully encrypted https, so DPI has to use very expensive (CPU + time) methods to see what the traffic maybe and this is not good for ISPs as its often more expensive than just assuming what it is by the IP address the packet is going to.
Look for obscuration