Oh boy, thats another can of worms. You dont happen to work for conformal do you btw?
So (it a long story) but a) no one knows who's funding them; b) most of them seem to have ex-defence contractor profiles; c) no one knows why they are coding it; d) if there is one off by even a single bit interpretation bug in it it breaks consensus and forks bitcoin, which can likely be systematically abused, to create a massive accounting/double-spend mess that will be too expensive to repair as last time - that could create a mega fork worse than the leveldb bug, and kill bitcoin or force some really harsh choices to best effort cleanup where there are innocent losers; e) it apparently took a lot of effort by the core devs to persuade them that this was a problem; f) it still has that problem.
d) This is a complete red herring and exists just as much with Bitcoin Core as it does with anything else. The exact same thing can easily happen (and already has as you've noted) with Bitcoin Core. This is a real problem with the technology that needs to be solved independent of the number of implementations on the network. In fact, working toward solutions which address this fundamental issue is necessary for Bitcoin Core too since it means mistakes there don't lead to undesirable consequences either. The current approach is "well let's just hope it doesn't happen!" and frankly, that just isn't good enough.
about why consensus is hard, and more so for two different implementations, here are two presentations first on language security as it applies to host security and software compatibility and second on bitcoin consensus. The first is quite eye opening even for security researchers (ie people who are experts in host security).
language security
https://archive.org/details/The_Science_of_Insecurity_bitcoin consensus programming
https://www.youtube.com/watch?v=on5ySFK0aoY#t=39m50sHave a listen, particularly to the first one and then we can discuss further (here or PM or bitcoin-dev or #bitcoin-wizards or whereever). I am genuinely interested to help resolve the discrepancy of opinion around this, as its actually to my mind significantly misunderstood, and dangerous for bitcoin.
Adam