You say "not quite as observant of the Prophetic example" yet that implies that the "Prophetic example" was understood in a monolithic manner. This is not the case, for even within a single "sect" you find a huge variety of understandings of both the example in question and what it meant for believers. While it is true that there was consensus on a few things (few would deny for example that the Prophet existed) outside of that there was a lot of diversity in interpretation and practice.

The most obvious example is that those we would now think of as "Sunni" and "Shia" sects began as trends in the conceptualisation of legitimate authority. That such a fundamental difference could exist is a pretty clear refutation of what you're saying here.

What in the Sunnah makes it necessary for tribesmen to be recruited that way? When in the life of the Prophet did he use enslaved soldiers from the steppes?

I know you're not a professional historian (and this isn't relevant to the truth or otherwise of my claims but I'm saying it anyway), but I am.

And your approach to this is not informed.

It is a true generalisation that the idea of the Prophetic example has had an ongoing importance for religious observance amongst Muslims, however your characterisation comes across as an ideological narrative rather than a reflection of the historical reality. Even if we assume that the beliefs/practices of the majority of Muslims are accurately shown by fiqh/aqidah texts: and were universally and prescriptively followed even such discussions vary widely in their understanding of the Sunnah itself.

Your analysis is being dunked on because it seems uninformed. If you read many texts of this period in the region you will find them arguing for the submission to a singular authority in the form of the Caliph, yet even a cursory survey of Muslim history shows that this was rarely even close to the case. That alone shows that it took more than an Alim to make a ruling to define something so complex as strategies of governance.

Living amongst Muslims doesn't equate to historiographical training. If this is a topic that interests you I would suggest reading scholarly works more widely.

"Not given much choice in strategy, because you're supposed to follow the Sunnah in everything"... what does this mean?

How is "the Sunnah" a strategy?