Yup that’s what I mean.
Seems like a reasonable limitation then (not that the entire business model of scientific journals is reasonable in the 21st century is reasonable - just this specific limitation). The journal’s theme is proprietary, but the paper’s authors still have the LaTeX source so they can just slap a free preamble on it and publish it with that.
If he thinks something doesn’t matter just because the people involved are dead, maybe history is not the right academic field for him.