[ballenf]

> One can conceive of other update rules. If one considers the five relevant cells...

I think they're looking at alternative update rules. The one you question ignores diagonals.

[symmetricsaurus]

Conway's Game of Life does consider diagonals. Since they start and finish by talking about GoL I think they've made a mistake.

[jeadie]

I can't believe I missed this. I always wondered why getting the types of patterns mentioned in literature were hard. Will definitely need to make an update. Thank you