ryans Yes. The youtube video is for convergence insufficiency. I train for convergence excess, so my eyes have to look through the card - I use a transparent fixed one with progressive difficulties https://www.good-lite.com/Details.cfm?ProdID=733. (I can send you the pdf with the card to be printed).
Ive gotten quite good, so I can now connect the circles and see 3d shape even with a non-transparent card. When I see the video, I can do both, connect them via crossing my eyes (converging) and uncrossing (diverging).
Seeing it sharp is another theme - accomodation. Maybe you can connect the circles, but you dont see it sharp.
My training is to be able to see sharp (accomodate) in full motion range, from convergence (which is easy, as I have excess of it) to divergence (the hard part).
You still should find a proper therapist. This needs controlled training, writing down results to know how youre progressing and where you should progress next, and so on.
Heterophoria is held in check by a fixation point - place the eyes can rest on. New tech/some software doesnt allow for a clear and stable one apparently, thus causing us problems.
I think if you have healthy eye teaming, the eyes at rest position overlap the image without the extra effort that we need.
Our eyes at rest position (no visual or light input, complete darkness) look like those of a person with strabismus.
This is a nice summary I just found: https://green-club.eu/wp-content/uploads/CET-51114-Investigating-and-managing-heterophoria-.pdf