I use to do something similar sometimes when I use a detergent I don't know and so of which I do not know the exact dose to use for me, but I get washer full of water and in agitation mode (lid switch pushed with a clothespin), I dissolve detergent and test with both visual (suds and water) and tactile (slippery water) if the amount is fine, and then still in agitation I add laundry...
Sometimes I just jump everything into and or put detergent in the basket along with clothes after having run some water, or also I put detergent in the pan in the filter-flo that acts as a dispenser also...
Without mentioning about the detergent dose in the video, that may be due for various reasons and that does not necessarily mean bad rinsing assured...
I think it's the most correct procedure for how I see things than just pour detergent into and most of all prior the laundry how is often suggested, sometimes infact laundry detergent may find it's way into washer piping and so pump (especially in some newer models having the pump block not driven by the motor power but in a box with a pump just for it).
In a couple of occasions while doing very short cycles I could notice at the first "gob" of water out of the drain some undissolved product...
So I think it's better having it dissolved before adding laundry or make sure it will not go and deposit into machine piping and pump at first run of water in the tub...
That's also why the same procedure was done automatically in some early front loaders and especially in some models constructa machines (before the later tub drain cup blocking system with the floating ball, or other methods used once)...they would have a bell telling when it was the right time to add detergent, and so when laundry was soaked...
Anyway, despite some instructions in some machines and detergents packages...some people do that for this reasons, others, especially older people do that because it was the method they used for wringer washers...
IMO is not wrong do this way, it's far more wrong jumping everything into and prior the laundry or prior having run some water to fill the empty pump hole/hose...
I'll tell you more...Dash Liquidtabs, used this matter to advertise the product saying that the pre-dosed cap would get rid of the unuseful waist of detergents ended in the washer piping (despite models of front loader from long now have devices to avoid this to happen)....
When using a fron loader I also followed the procedure of having run water for some seconds (you never know), and the I would fill the dispenser, close it, re-open after awhile to rinse the outer drawer bottom body from detergent poured inside from dispenser and then unrinsed because under then drawer compartment...
If filling time was alredy finished, I used to fill a cup of water and have it manually poured inside to rinse, or waited the second filling phase (of water level adjustement in case of full loads)...
That's it...