This is a case of an unwisely chosen simile taken waaaay too
far. This idea, that the entire universe could be inside the
event horizon of not a supermassive, but rather a
superduperultrahypermegastupendouslymassive black hole, is
usually introduced in introductory classes about general
relativity. The instructor in this case is trying to make clear
that, contrary to a fairly popular misconception, the event
horizon of a black hole is locally flat. That is, there are no
CGI-fireworks, nor any kind of hard "surface", nor anything else
particularly special, in the immediate vicinity of the event
horizon. The only special thing that happens is a long distance
effect, like noticing that every direction now points off in the
distance towards the singularity. The simile is also used to
point out that, at the event horizon, even second-order, nearly
local effects (that is, curvature of spacetime, or tidal effects
in other words) become less pronounced the more massive the
black hole is. (As an aside, this also expla