aspect_ratio not working expectedly with PGFPlotsX

Details

When plotting heatmap with PGFPlotsX backend, I want to have aspect_ratio = 1. The following script

using Plots
pgfplotsx()

heatmap([1, 2, 3, 4], [1, 2, 3, 4], [1 2 1 0 ; 1  3 4 5; 1 0 0 1; 1 9 0 8], aspect_ratio = :equal)  

gives the following figure: The x axis of this plot is of course too wide; but then, the following script aimed to solve the problem by fixing the x range eliminates the effect of aspect_ratio = :equal:

using Plots
pgfplotsx()

heatmap([1, 2, 3, 4], [1, 2, 3, 4], [1 2 1 0 ; 1  3 4 5; 1 0 0 1; 1 9 0 8], 
aspect_ratio = :equal, xlim=(0.5, 4.5))

By inspecting the LaTeX code generated, the problem seems to be that heatmap, when asked to generate a figure with aspect_ratio = :equal, simply adjusts the scale of the x axis so that the main body of the heatmap becomes a square; but this is not what is intuitively expected: there is an axis equal image option for the axis environment in tikz, and, IMHO, this is what should be invoked when the aspect_ratio = :equal option is used.

Backends

This bug occurs on ( insert x below )

Backend	yes	no	untested
gr (default)
pythonplot
plotlyjs
pgfplotsx	x
unicodeplots
inspectdr
gaston

Versions

Plots.jl version: [91a5bcdd] Plots v1.36.1 Backend version (]st -m <backend(s)>): [8314cec4] PGFPlotsX v1.5.1 Output of versioninfo():

Julia Version 1.7.3
Commit 742b9abb4d (2022-05-06 12:58 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, tigerlake)