I don't think the primary counterargument is tech progression, I think the primary counterargument is that decoherence as defined here, and tech debt in general, are usually a function of humans balancing work time vs deliverable demand (for coding), and making tradeoffs like those adhoc patches vs rebuilds-to-maintain-coherence... but that is not intrinsic to coding, and is much less relevant to an agent swarm who could feasibly decide that a full rebuild using the lessons gleaned about design, but without the actual code debt, is warranted and possible within a short time window.

If a cyclical process of n iterative updates > rebuild back to coherence > n iterative updates > rebuild back to coherence etc is used, you could mitigate the exponential loss of coherence, provided you set some kind of baseline for what rebuilds produce.