I think your over exaggerating the issue. They did release the bamboo back, and then later pulled it from the market because there was a problem. Perhaps there was a design flaw that was overlooked when testing the device that simply cannot be fixed on the current hardware design? Or perhaps they simply haven't yet figured out a solution?
If they had said they were going to do it, and then just 100% ignored it and never even attempted to deliver, that would be an outright lie. The actual scenario is that they did deliver on that promise, and something went wrong. A lack of solution to an unforeseen issue does not make it a lie.
EDIT: Some quick googleing proves this exact scenario: http://www.androidauthority.com/oneplus-swapstyle-covers-526908/
The replaceable back caused integrity issues with the device. Again, they obviously cannot redesign and recall the device. Oneplus almost certainly doesn't have the cash for that, nor would it be a justifiable expense if they did given how few people would care. It was an unforseen design flaw. Nothing more, nothing less. That doesn't make it a lie. You're grasping at straws for calling the company dishonest over something this minuscule.
They just got in over their heads and can't meet production or expectations in most anything as it sounds like they are terribly understaffed.
I did have a bamboo back and also have an extra white and black. The cover is just slightly harder to take off than a Samsung back. I just use my fingernail and it comes off in less than 30 seconds.
The nonsense about potential risks to the battery is just that. It's no different than any other battery and unless you remove the cover in the shower or while swimming in the pool I don't see what extra risk there is.
Oneplus has produced a great phone but they do have the tendency to stretch the truth or lead you along. They might not be outright lying but definitely use word play to the fullest and love to use social media to stir the masses on the OnePlus forums.
From the article:
Taking to its forums, OnePlus has announced that it is canceling its SwapStyle line due to production issues and the fact that they could have designed the removal process of the back covers better; its tricky and makes frequent switches difficult. The swap can also leave the back cover slightly creaky or loose, and it risks damage to the battery which is exposed for a short time.