Is there a particular reason you would bet against it, or do you just saying that you wouldn't would bet for any implementation without proven theoretical properties?
(As an aside, it's probably just my lack of familiarity, but considering how simple the algorithm is I find the syntax surprisingly hard to follow. Is this modern C++?)
Although this thing is able to fool the 200 or so tests from TestU01, it would take a short time for an expert to devise a test that would distinguish it from random, and even recover the key (read: seed). On the other hand, AES-CTR (conjecturally) fools _all_ statistical tests that take less than 2^128 effort, and on top of that it is still very very fast (0.63 cycles per byte on Haswell). So what really was gained? Cryptographic primitives have gotten so fast that the additional speed from these ad hoc generators seems like an unworthy risk. I concede that it can be very fun to try to make them, though.
Additionally, a generator that passes those 200 tests is not guaranteed to be high-quality for a particular usage, which might as well be considered nothing but another statistical test. There is the famous case of the r250 generator---an additive Fibonacci generator that passed all statistical tests of the time---which turned out to have characteristics that rendered costly real-world simulations wrong [1].
That is C++, yes, but I don't think there is much of anything modern about it. Trying to save on space probably contributed to its unreadability a bit.
I know this paper, and like this approach. Reduced-round primitives let you take advantage of existent analysis, and keep some guarantees while improving speed. In the case of AES, we know that the probability of any differential for 4 rounds is at most 2^-113; similar for linear probabilities [1]. I'm curious why ARS-4 fails Crush; I wonder if the custom key schedule is the culprit.
(As an aside, it's probably just my lack of familiarity, but considering how simple the algorithm is I find the syntax surprisingly hard to follow. Is this modern C++?)