For example, if we started a human-level AGI tomorrow, it's ability to revise itself would be hugely limited by our slow and expensive infrastructure (e.g. manufacturing the new circuits, building the mainframe extensions, supplying them with power, debugging the system).

This suggests that he see the limiting factor for AI to be hardware, however I've heard people argue that we probably already have the hardware needed for human-level AI if we get the software right (and I'm pretty sure that was before things like cloud computing were so easily available)

I wonder how likely he thinks it is that a single organisation today (maybe Google?) already has the hardware required to run a human-level AI and the same speed as the human brain. Assuming we magically solved all the software problems.