No. No. No.
The difference is that production quality software needs to be usable by other people -- often many other people -- instead of just the author or a small group of researchers. In many cases it must work close to 24 hours/7 days per week under highly variable conditions.
This means it generally must have fewer and less severe bugs than a proof-of-concept or research prototype. This often requires extensive testing by end users or QA folks standing in for end users.
There are many examples of shipping commercial products and widely used open source programs that clearly meet this criterion but are certainly not easy to read, maintain or extend code.
Modularity in particular often fails to produce either readable or extensible code, rather producing numerous layers of confusing modules and/or objects -- "lasagna code" instead of "spaghetti code." It also can fail to produce "production quality software" as I define it above.