However he uses a very different tactic from what I am used to. He makes separate schematic symbols for all the capacitors and resistors, why is that?
It feels as if that would not be good for productivity and it inhibits the use of generic libraries?
I have not watched the video but suspect it is because a different footprint was used for each capacitor (& each resistor). If you don't do this & later invoke the command to update all components from the library, you will end up with the generic (standard) footprint for that schematic part for all your capacitors (& resistors).
The approach that Altium has taken for many years now is to provide you with an extensive set of "unified libraries". Altium expect you to specify a part from a particular manufacturer, search for that part in the extensive libraries using the full part number, select it & place it into your schematic. By using this method you are guaranteed to also have the correct footprint.
You will notice in the latest version of DipTrace gives you a generic library containing (for instance) all the TOxxx through hole & SMD parts. You can select a different footprint "on the fly" when laying out your schematic & this is remembered all the way through to the pcb layout.
I'm the same as you, preferring the DipTrace way of doing things, but Altium use their unified libraries as a selling point & a way to continually getting their customers to pay for another upgrade.
ADDED:
Target 3001 have a great idea of running all components in one large library. Runs well when it just contains the generic footprints plus a few special ones you have added yourself. No need to locate & add the required library to then have access to the one footprint you require.
Altium can't do this as they have hundreds of thousands of parts, all with specific part numbers. If you opened all the unified libraries at once, your computer would slow to a crawl. So, Altium had have to resort to users installing (say) 15 or 20 libraries during the schematic design stage to have access to the schematic & footprint parts. Altium then let you save just the parts used into a separate library to minimise the RAM required by your computer & to provide you a small file to save alongside your schematic & pcb files.