If that's critical thinking, then I'm a banana.
How does this guy get to the conclusion that 'John' was a witness to Jesus' miracles and resurrection?. We hear some talk about "the disciple whom Jesus loved" (unnamed, and spoken of as another party). Who 'we' may be in the final episodes of the gospel is unclear. Maybe that writer had royal delusions and meant it to refer to him or herself.
I had a read of one of the article's links:
The Circumstantial Case For John’s Authorship. He sets out the reasoning of Max Andrews on who wrote John.
It starts with 1:14 "we have seen his glory", then 2:11 "[by turning water into wine] he thus revealed his glory, and his disciples put their faith in him". So the "we" is his disciples: as the reference to 'his glory' shows.
He then continues to identify John as the probable author by a process of elimination of the other disciples, using references to 'the disciple whom Jesus loved'.