In the Pool School article How to Chlorinate Your Pool it says the following about Dichlor:
Dichlor should never be used for shocking unless the CYA is VERY low. For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm. The same article talks about Trichlor as follows:4. Dichlor - Somewhat less common than the three forms above, dichlor contains both chlorine and CYA. Easily dissolvable, it is an excellent shock source of chlorine as long as your pool doesn't already contain too much CYA.
Here, it is very clear that Trichlor builds up CYA. The same is true for Dichlor, except it's even worse (i.e. a more rapid increase in CYA for the same FC addition).2. Pucks - (trichlor) Solid round discs that you simply put into an automatic container that passes pool water over them and they slowly dissolve - putting chlorine and CYA into your pool. They are incredibly convenient and incredibly insidious. The CYA that they put into your pool water never goes away and, in fact, continues to build. Building often to a point that it can render your chlorine ineffective. You start to develop algae and don't understand why.
In the Pool School article Definitions and Abbreviations, it says the following about Dichlor:
where it is very clear that it should not be used as 'shock'.Dichlor
A stabilized, granular, fast-dissolving form of chlorine (chlorinated isocyanurate). Because of it's fast dissolving nature it is sometimes sold as 'shock' (not a good idea since it will raise CYA levels fairly quickly). It is mildly acidic and will lower pH and TA. Causes CYA to rise with continued use so it is not a good choice for those with cartridge filters or in climates that do not winterize pools and have an extended swim season. It will add .9 parts CYA for every 1 part chlorine it adds.
I suggest fixing the "Hot to Chlorinate Your Pool" article so that it does not suggest using Dichlor for shocking.