Just an ordinary transformer with parallel windings. There is nothing wrong with parallel windings as long as they are as near identical as possible so they carry the same current and create/receive the same magnetic field. It is a trick used sometimes in high current applications where a single thick wire would be difficult to bend cleanly around the core.
It has nothing to do with the main topic of the article which is about simulating the PNPN structure of an SCR by connecting a PNP and NPN transistor across each other.
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Brian.