We can go about this all day David, but I think we both agree on some things here.
1) anyone can contaminate a starter as you described and no doubt it could change.
2) a properly or routinely maintained starter is not likely to be overtaken by dormant yeast in the flour.
Do you agree with these statements? If so, this is not what Brian posted. Brian states that ALL starters no matter the origin will be taken over by local yeasts within 2 weeks. Of course I'm paraphrasing here but his statement is with the understanding of routine use and maintenance, not left to die and then add a bunch of crap into it. And I am sure Brian is not walking around with starter in his back pocket either.
I'm not saying starters are indestructible. They are hearty for sure but you can kill one if you intend too. But for routine use at room temps and /or storing it in the fridge, I contend that you can easily maintain the original starter. Easily...there is not a chance it will be overtaken with routine use.
BTW, even an over ripened and neglected starter that has been dormant in the fridge for 2 months will revive to it's orginal state within 4-5 feedings (less than 24 hours) and not taken over by yeasts in the flour. I can revive an old decrepit acidic starter in less than 24 hours, a much shorter time frame that it takes to create a new starter from yeast in flour which takes me 6-7 days to propagate.
I'm curious if you have 1) revived a starter from the dry state and/or 2) have created a starter from scratch. How long does it take you to reactive a dry starter vs one made from scratch?
And just for clarification, what do you consider is proper maintainance of a starter?
If it is true that All starters will be changed to local floral within 2 weeks, then any routine for maintaining a viable starter will suffice, as it won't matter what the routine is anyway. But if the starter will maintain it's orginal characteristic flavor, despite varying maintenance routines, then my point proven even more so.