I have not heard about the H chassis being more reliable than the I chassis, they should both be similar. The only difference is that the I chassis combines the SPU2 and DEV9C into a single chip and has a different clock system.
I did some more internet research but didn't find any claims that the I chassis is more reliable than the H chassis, except for Google's AI which claimed the I chassis was more reliable, and describing the I chassis as a "Slim" PS2 (which is totally wrong because the I chassis is a FAT PS2 and also Slims are considered less reliable than most FATs in general). So I'm not sure where you have read that, other than the incorrect AI.
