I am exactly how he describes. I cannot visualise anything and I don't have an internal voiceover. I do however recall abstracts and concepts. So if I saw an elephant before I'd be able to bring up the concept of the elephant. Nothing visual, but conceptual. I've discovered this is a thing (that people actually visualise) past my 40s. For a while I thought I missed out on some special fx, but it had no detrimental effect on my life. Maybe even it does help me see complex software as abstracts easier. Who knows. It is what it is.