Does this count as a Malthusian catastrophe even though the food was ample?

Limiting factors are the things you don't have enough of.

If food isn't constraining, it's not your limiting factor, something else is.

The general idea is expressed in Leibig's Law of the Minimum, from Justiz Leibig, a 19th century botanist.

This is why counterarguments to Malthusian philosophy based on showing that some arbitrarily selected factor isn't constraining are moot. The question is, what is limiting in the environment. And if growth has stopped, something is constraining it.

I suppose? Running out of physical space is almost as bad as running out of food, physically and psychologically speaking, unless you're very heavily adapted for it.

Space was a limiting resource; mice who were breeding were fighting neighbors for nests.