But the Malthusian argument is basically saying better that they die now to expedite growth later?

If one believes that it is better, for the individual or the group, to die in war or acute famine than to live malnourished, then peace and a stable food supply may be bad (but then one should apply the reversal test and ask such people whether they support war and high variance food supply).

But disease is not like war or acute famine. The survivors are often permanently affected, in many ways like the malnourished. So many arguments that consider malthusian conditions should support medical aid.