Answer supplied above (spoilered) by Vipre as to why Goo Chirons end up harmless. But they’re dangerous - more than worm chirons - and can ruin your day even if you don’t rely so much on mobility (personally, I play a very mobile tactics).
I thought that Pandorans in different areas seem to favour slightly different tactics. Or maybe not, and it’s just my cognitive bias. But in my game I found the Pandoran attacks in East Africa seemed to keep spawning Goo Chirons, but the ones in North America tended to Worm Chirons. It took an incredibly long time until I found Worm Chirons that fired poisonworms or acidworms, too.
I might be wrong, but I might have got the goo tech from capturing a Scylla with poison spit, as that also goos.