It is one thing to argue with the claim that models are alien to Marxism, but to say that it is bizarre, is, well, bizarre. It is not bizarre; it is an argument that you don't accept.
Grossman's extension of Bauer's 'reproduction scheme' caused a lot of misunderstanding of Grossman's argument. For the sake of argument, Grossman extended Bauer's version of Marx's 'schema' of reproduction (incidentally, the schema of reproduction in volume II are the closest to a model in marx's theoretical reconstruction of capital, which is why he is rather apologetic about using them).
Bauer's reproduction schemes themselves are a messy confusion. Marx abstracts from, or sets aside the impact of accumulation on profits in the reproduction schema to show that beyond the ratio of surplus value to Capital, there are distinct limits to the proportions of the two (main) departments of capitalist production, production of means of consumption, and production of means of production. These limits are entirely to do with the necessary proportionality of the output of these two departments to the proportions of variable to constant capital. Marx's schema were widely misunderstood because he seemed to show that capitalist production had no limits. All that he really showed in the reproduction schema was that SETTING ASIDE THE FALLING RATIO OF SURPLUS VALUE TO TOTAL CAPITAL ADVANCED it was possible to extend reproduction into the future indefinitely, so long as the correct proportions between the two departments obtained. I.e. Marx was showing that the limit to capitalist accumulation WAS THE THE FALLING RATIO OF SURPLUS VALUE TO TOTAL CAPITAL ADVANCED.
Bauer confused the issue by putting the ratio of surplus value to capital advanced back into the schema of production. Thereby he demonstrates that capitalist accumulation can go on indefinitely. Grossman, for a joke, really, showed that even if you did follow Bauer's method, then breakdown would occur (in the 34th year, if memory serves me). But Grossman's playful extension of Bauer's schemes of reproduction was widely assumed to be an attempt to demonstrate, through the schema, that capitalism had a definite shelf life. That was a misunderstanding. Grossman was only trying to point out that EVEN ON BAUER'S OWN TERMS he could not show that accumulation would continue indefinitely. But that was not Grossman's proof of the inevitability of breakdown, which was the conventional marxist one of the falling rate of profit consequent on the overaccumulation of capital. The general view that Grossman was trying to prove the inevitability of breakdown through the schemes of production is a confusion that he sowed, by his somewhat self-indulgent showing off.
All of which demonstrates not the centrality of model-making to Marxist social theory, but the problematic character of model-making for Marxist social theory.