It’s not a consensus at all. The reason why the FLRW model does not include modelling boundaries is because it is very hard to model boundaries, not because they are unlikely.
Assuming a finite universe, the universe can either have an edge or no edge. Many finite mathematical spaces, e.g., a disc, have an edge or boundary. Spaces that have an edge are difficult to treat, both conceptually and mathematically. Namely, it is very difficult to state what would happen at the edge of such a universe. For this reason, spaces that have an edge are typically excluded from consideration.
to respond to your pocket universe theory,
It’s not my “pocket universe theory”. It is the theory of Infinite Inflation, the most popular version of the standard model.
That doesn’t mean there can’t be other universes though.
Those “pocket universes” are not really other universes. They are physically connected to our universe. They are called pocket universes because they are too far away to communicated with. The depiction I showed you is not an abstraction, it is what is believed to be the actual geometric shape.