That's not at all what he way saying. In the conclusion at the end of the article he said that "I therefore no longer consider Table 1-1 in Test-Driven iOS Development to be representative of defect fixing in software engineering [...]".

So while the data might still be true, the numbers are not necessarily accurate and thus you shouldn't base conclusions on that table. He doesn't say that the values are wrong - just that they might be incorrect.

On a related note: I'd love to get real numbers for this. Fixing bugs happening in production certainly feels much more expensive and cumbersome, but is there real data aside of this table which now apparently is inaccurate.

Well, that was what I gathered from the part I'll about to quote. But considering English is not my native language I might have misunderstood his meaning:

"As explained in the book, this table is reproduced from an earlier publication:

    Table 1.1, reproduced from Code Complete, 2nd Edition, by Steve McConnell (Microsoft Press, 2004), shows the results of a survey that evaluated the cost of fixing a bug as a function of the time it lay “dormant” in the product. The table shows that fixing bugs at the end of a project is the most expensive way to work, which makes sense…

The first mistake I made was simply that I seem to have made up the bit about it being the result of a survey. I don’t know where I got that from. In McConnell, it’s titled “Average Cost of Fixing Defects Based on When They’re Introduced and Detected” (Table 3-1, at the top of page 30). It’s introduced in a paragraph marked “HARD DATA”, and is accompanied by an impressive list of references in the table footer. McConnell:

    The data in Table 3-1 shows that, for example, an architecture defect that costs $1000 to fix when the architecture is being created can cost $15,000 to fix during system test.

As already covered, the first problem is that I misattributed the data in the table. The second problem, and the one that in my opinion I’ve let down my readers the most by not catching, is that the table is completely false."

He didn't say it was false. He did say it was unsupported.

"The second problem, and the one that in my opinion I’ve let down my readers the most by not catching, is that the table is completely false."

"it" meaning the conclusion about the exponential increase in the cost of fixing bugs over time.