when does :cache not cache?

[Eric S Fraga]

Hello all (again!),

in the paper I am writing, I have a number of gnuplot src blocks, some
of which process a significant amount of data so take some time to
generate the actual plots.  The data are static so caching the results
make sense.  However, even though I have ":cache yes" on each of these
named src blocks, and I have (for good measure), the property
"header-args:gnuplot" set to ":cache yes" as well, the plots are being
regenerated each time I export to PDF via LaTeX.

In trying to create a minimal example (see attached), it seems that
caching stops working as soon as I add a ":var data=..." header argument
to generate a plot from a table of data.

Why does specifying a variable to a src block violate the caching
directive?  Is this intended behaviour (assuming I've understood what is
happening correctly)?

Thank you,
eric

-- 
: Eric S Fraga via Emacs 28.0.60, Org release_9.5-163-g4eab5b
: Latest paper written in org: https://arxiv.org/abs/2106.05096

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