Hello Efthimios,
Good question. What I claim, and the reason I believe my model is stronger than claiming directly that the world is digital, is because in my view one doesn't have to presume discreteness as a basic assumption of the world. One starts asking how the universe looks like in terms of the distribution of patterns in the world. Then one can conclude either that the world is digital because it looks like so (or does not), or that it is algorithmic (in the digital sense) even if it is not digital, case in which I argue we have no reasons to think it is not digital. We provide some evidence in favor of the resemblance between empirical and digital datasets and means to continue the investigation (investigation that has already provided some applications by the way, such as the calculation of the complexity of short strings where compression algorithms use to fail).
You may also mean that the world could be algorithmic in other different sense, in an analog fashion (in the sense of being carried out by an analog computer) and still remain algorithmic. It could be, but so far we have had a hard time trying to define analog computation, at least in feasible terms, and our best model to understanding the world has turned out to be digital (Turing) computation. This is why I focus on discussing the way the world seems to unfold and whether it may do so in one or another way. Our claims are supported by statistical results (statistics are not proofs though), and we found that patterns in the real world and the digital ones, that we simulated, seem to be distributed alike.
Among the things I argue in my essay is that the world would have greater chances to look random (or more random if you prefer) if it were analog. If one throws digits into the air of an analog (infinitely divisible) world and if this hypothetical world allows 'true' (indeterministic) randomness unlike in a digital one, then one would expect every digit to be like the digits of a Chaitin Omega (see definition in the Appendix of the essay), this is a number that is random by definition under our standard model of computation. You can perform the same thought experiment with a real number line and see that chances of picking a random number among all numbers, in a finite interval, is 1, that is complete certainty that you will pick a random number. Yet we don't experience that in our everyday life, but quite the opposite. Chaitin has proven that one cannot calculate most digits of an Omega number (for some Omega numbers not even a single digit), so in a world where random numbers persist, things might just have greater chances to look like Chaitin Omegas. The fact that we can do science in this world seems to be an indication favoring that this is not the case.
You are right, it is very interesting how physical models based on mathematical theories assume continuous variables, yet when one solves the equations of, let's say general relativity to take the example you mention, the model becomes algorithmic in the strict digital sense, either by the mechanistic way in which equations are solved by hand, or literally when solved by a digital computers. The algorithmic view might turn out to help as a shortcut to understanding the digital nature of the world without having to assume it at first.
Sincerely.