“Some(one) misguided them into thinking it is legitimate. “
I happen not to use the eruv, but for the record, there are numerous, very choshuve rabbonim who give it the green light.
That being the case, the backup eruv is meant to do just that; back up the “main” eruv. Most likley, it was done to prevent sabotage from downing the eruv 20 minutes before the zman.
And yes, there were people who did such a thing. I know, because I know. Fact.
If you carry, you have on whom to safely rely on. But, the people who give the heter on the eruv, have a whole host of things they are machmir on (things, that many of us would sorely miss, if we needed to choose a new hadracha).
All things being equal, I’ll stick to a 6 day carry week. The price for switching is too steep IMHO