imod.idf.open gives a somewhat confusing error when inferred dimensions and coordinates do not align

Taking this LHM inspired example:

IDF files:

budget_1_20000101_l1.idf
budget_1_20000102_l1.idf
budget_1_20000103_l1.idf

budget_2_20000101_l1.idf
budget_2_20000102_l1.idf
budget_2_20000103_l1.idf

budget_2_20000101_l2.idf 
budget_2_20000102_l2.idf
budget_2_20000103_l2.idf

Opening with riv = imod.idf.open(path_riv, pattern="{name}_{sys}_{time}_l{layer}")

Results in an error that is not maximally clear:
ValueError: conflicting sizes for dimension 'layer': length 1 on the data but length 2 on coordinate 'layer'

This makes you think there's something wrong with the layer, but it's really the created sys dimension that is probably not desirable.
This is an xarray error, raised here: https://github.com/Deltares/imod-python/blob/8b266c431486436cb2d018e3c23c1f59b4e89b2f/imod/formats/array_io/reading.py#L322

What happens is that sys1 has data for only one layer, but sys2 has data for two layers.
It's a bit hard to debug in this case, because the error is relatively short.
It might be clearer if it stated: Attempted to create DataArray with shape (...), dimensions (...) and coordinates (...) or something like that.

Start in imod/formats/array_io/reading.py around line 322 and reproduce the listed imod.idf.open call with the sample IDF layout. Update the resulting error so it identifies the mismatched inferred dimensions and coordinates, especially sys and layer, then verify the example reports the cause clearly.