That exact phrase pops up a lot (like it gets pasted verbatim around the net) but I've yet to see any evidence to corroborate it's even true. Where as it has been widely reported by a number of independent sources (Beck's family, the Transport for London, etc) that Back's plans were based on circuit diagrams. So I have a hard time believing the 'myth' argument is more trustworthy.

Please also note when they talk about Beck's inspiration they say "circuit diagram" and not "circuit board", like the paragraph you quoted.