The truth is the same in both cases: sometimes "deleted" data is actually deleted, and sometimes it isn't. The difference is perspective: the user wants "deleted" data to be deleted and forensics people want it to be preserved.

Both. Yes, they're arguing from different positions.

With a magnetic disk it's straightforward to force data be overwritten at a physical level. With an SSD it is less straightforward and it may not be possible to ensure that the data from a particular file has been erased.

So from the perspective of a diligent user an SSD is riskier than an HD.

However, typical usage of a hard-drive will leave a significant amount of "deleted" data still on the drive, except for unusual circumstances (such as subsequently using the drive to near capacity). While typical usage of an SSD will tend to erase most data fairly soon after it has been "deleted".

So from the perspective of a non-diligent user an HD is riskier than an SSD.