Maybe the reason might have been an attempt to ensure that a relatively high percentage of AI corps/armies would have at least one Engineer brigade per merged units. So AI file preparer made all year 1936 AI files to prefer Engineer brigades - which was meant to offer a base layer of land units with an ability to provide a valuable dug-in bonus to other units that would be merged with them in a future. (Although I don't know how the AI's unit merging mechanics exactly works.) It might have been expected - since the switch parameter is set to "no", then one could say incorrectly so - that at the latest in 1939, based on the year 1939 AI files, but for many AI nations even earlier (thanks to the event driven, build schema altering AI files) an AI would start to produce land units with a wider range of brigade types - as specified in files - that would form effective corps'/armies with previously built units (with Engineer brigades) evenly spread along the fronts. (But as the switch is set to "no", possibly mistakenly, other brigades actually never are build.)