Not at all. The questions are 1) does the method described sound reasonable and 2) if I implement the same methods, with my toolset, and process the same data, do I get the same result?
If the results are different, using different implementations of the same methods, then it's possible that either party could have the error. But if the second party is reusing well-tested code of their own, or something from Matlab or whatever, then it is more likely that the unknown code of the original lab is the problem.
You might have a point about a simulation, but an awful lot of science isn't simulations, it's analyzing recorded data.
(Ex: http://www.plexon.com/product/Offline_Sorter.html#Features)
Given a terabyte of recording data, I'd think it should be sufficient to specify the parameters they used for spike sorting. Someone else ought to be able to use a different package on the same data and obtain results similar enough to know if the first person fudged their paper.
Given a set of data, and a named algorithm, it ought to be possible to obtain the same result with any correct implementation of that algorithm.
Is your paper nothing but off-the-shelf "spike sorting", or is that used as a component of something larger? Rolling back around to the original point of source code release being a desirable thing, if it's the latter, just knowing that this one library was used from what is probably literally a single sentence in the paper that reads "We used spike sorting software X to obtain sorted spikes", when presumably the library has knobs whose settings you don't know and you still don't even have their raw data to check the settings with, you still know virtually nothing about what was actually done. Source release ought to be standard.
The degree to which people who are putatively scientists will go to bat to defend making it difficult or impossible to replicate their experiments boggles my mind.
Besides, the code is almost always worthless compared to collected data. What would actually be most valuable and practicable is for groups to be running their proprietary code on each other's public data for confirmation.
Further, the Kolmogorov complexity of a simulation is typically a wee bit larger than the Kolmogorov complexity of a square root implementation. That metaphor is beyond useless, it's deceptive.