I have not seen the video mentioned.
Using a stirrer can keep solids up off of the bottom of the heated boiling reaction vessel, when these powders that form and settle on the bottom of your reaction vessel, can create hot spots or uneven heating of glass-ware, causing the glass to crack or break, another problem is called bumping where gases form under these powders try to get out from under the powder and do so fairly violently, almost bouncing the glassware. The use of a stirrer is a good Idea for many of our lab work, if I had one I may have saved a few of those cracked coffee pots I have had in the past, a heated stirrer is something on my list of things to get (someday).
The rock salt would not form as tight of a cake of powder in the bottom of the boiling vessel, and should not contain Iodine, that many table salts can have added, I am unsure what anti caking agent would be added to table salt, I do remember using rise to keep the salt dry and from the moisture absorbed from the air from making a solid lump of salt in the saltshaker.
Iodine has a higher boiling temperature and I do not believe it would boil over in condensate, but I do not know for sure if compounds would distill over or not, but iodine can dissolve gold, so it would just be best not to use iodized salts to make your HCl.
, I found out the anti caking agent was silicon dioxide, so will avoid unless advised otherwise.
