label font for colorbar is smaller than FONT_LABEL?

I am using GMT 6.5.0 so apologies if this is already fixed (or not a bug).

**Description of the problem**

When setting the font size for my colorbar label with ```--FONT_LABEL``` it renders as smaller than if I used the same font with pstext. Is this intended? I can _change_ the size with ```--FONT_LABEL```, it's just that the actual sizes don't seem to match up.

(From testing it seems that setting axis labels on the main plot, e.g. in ```psbasemap -Bx+l```, results in the same size text as pstext gives me, so it is colorbar that is producing a smaller font than specified with FONT_LABEL.)

**Full script that generated the error**

```
gmt begin labeltest png
gmt grdimage @earth_relief_01m -R-10/10/48/60 -Coleron -JM10c -BneSW -Bxaf -Byaf
gmt colorbar -Bxa1000+l"Elevation (m)" --FONT_LABEL=20p,Helvetica
echo "Elevation (m)" | gmt text -F+f20p,Helvetica+cBC -D0/-3c -N
gmt end
```

**Actual outcome**

**Expected outcome**

I would expect the two lines of text saying "Elevation (m)" to be the same size, since they are both set to ```20p,Helvetica``` as far as I can tell.

**System information**

* Operating system: Debian GNU/Linux 12 (bookworm)
* GMT version (`gmt --version`): 6.5.0