Ethan Merritt - 2017-01-24

Aquaterm output is rather limited compared to other terminals.
No one has ever put in the work to implement point-drawing code specifically for aquaterm, so all you get are the 6 generic point types you see in your test output.

I suggest using one of the full-featured terminals like wxt or qt.

I don't really know how much work it would be to modify aquaterm. It is a separate project from gnuplot, although historically related. You could try asking via their project pages
https://sourceforge.net/projects/aquaterm/
https://github.com/AquaTerm/AquaTerm