The GI solver only outputs very low resolution light maps for me. Here is a screenshot[i.imgur.com] of a very simple test map with baked lightmaps in the Talos Principle Editor and here is a screenshot[i.imgur.com] of an identical map in SS3 Editor. As you can see, the talos one is only something like a 16x16 texture, while the other shows the full 512x512 pixels, as i have set it in the lightmap option (this corresponds to what is rendered in-game of course, it's not just the preview).
This is likely related to some GI solver problems that I'm having; the editor crashes almost every single time I after it's done baking the lightmaps. When I reopen the editor after it crashed, I can import the solution, but the results are low-resolution like you can see in the screenshot above.
Here are the logfile of the GI solver[mega.co.nz] and the logfile for serious editor[mega.co.nz]. I opened the map from above, baked lightmaps (didn't crash on the first time, but showed errors in the console), baked again and the editor crashed.

Note these lines:
I guess it looks for some parts of the lightmap that was never created due to the GI solver crashing or something along those lines.

Also note that this map is just a minimal example of the problem, I get the same result with any other map, including the one I uploaded to the workshop (although that one doesn't show any lightmaps at all despite me baking them; importing the solution works, but it looks like crap due to the low resolution).