Why are you importing the gerbers? ST provides the native .pcbdoc in what they label "schematics" on their website.
Main reason is probably that I'm overwhelmed by the documentation.
I went back and the page for that Nucleo board does not load properly today, so I also only had the .pdf of the schematic.
I also went back to look around a bit more and found the b-g431-esc1 I downloaded all design files for that project without a hitch, and can also import the PCB into KiCad without problems (Including complete 3D view with all the parts).
This board does double or triple duty for me, as I'm interested in both STM32, motor controllers and their design, altium import in KiCad.
And I must say I'm thoroughly impressed in lots of different ways. By ST by making such boards available and amount (and quality!) of their documentation, for KiCad for their import quality.
But I'm trying to limit my KiCad raving in this altium section, so back to the original topic.
The chip footprint for the G432-ESC board has a perfect metric pitch. Pads are 0.3mm wide and with a clearance of 0.2mm, so apparently there is just something strange with that Nucleo-144 board.
... half an hour later...
I also had a look at this MB1035:
Design files available, imports into KiCad, Only two layer That other nucleo board was 6 layers) and the tqfp 100 footprint is quite differently designed. Pads are narrower, clearances are wider, and the "corner pads" are bigger then the others. But to keep on topic The pitch of this one is also nicely regular, which confirms again that the other board just had a weird IC footprint.
https://www.st.com/en/evaluation-tools/stm32-discovery-kits.html#cad-resources