Gas Giants Converting to Terrestrial Giants When Colliding

[Gregory]

I was experimenting HAT P-67 b and XO-2 b (the 2 largest known planets) colliding to show the effect of their mass and radius change, and I saw that XO-6 b briefly started showing a terrestrial texture.
This has to be a bug because there's no way gas giants could look rocky when colliding unless they're stripped of their gaseous layers, leaving behind their dense cores.

[Gregory]

Plus, when I experimented collisions with Jupiter with other planets (including more Jupiters), Jupiter ended up showing a terrestrial appearance despite not having enough mass to behave as a terrestrial of that size.