I'm not interested in getting into a huge argument on this, the post is my opinion take it as you will. I will note that as someone who has worked specifically with both the social sciences (including post modernism) and quantum mechanics I am actually quite familiar with both and I stand by my statements.

But hey lets go a little further because, its the internet why not there's no page charge here...

Heisenberg postulates a very specific mathematical formulation for a core quantum phenomenon. While there is no exact equivalence in social science research, phenomenon like WEIRD are reasonably close parallels in terms of the attempts to control for one phenomenon having impacts in unintitive or counterproductive ways that impact the search for truth.

Further, I, as someone who works in technical education (and who is also an engineer), find conceptions of truth such as the one you imply deeply problematic. I see them as a concern for the future of technical fields and technical personnel. Look at the impact of design and design thinking on many fields. The search there is less interested in truth and more in meaning. I suspect that your misconception is related to fundamental questions about the difference between truth and meaning. Post modernism doesn't try to make truth subjective, it fundamentally rejects truth (largely in favor of meaning). Post modernism began as a rejection of the modernist ideals that we could find with absolute certainty. This is not the realm of 'scientific' (i.e., convergent closed form solution). The questions, and therefore many of the answers, are not tractable in a mathematics sense and work is typically on finding a tractable form that serves as a reasonable approximation rather than a tractable, single, answer.

The difference is one of abductive vs. deductive/inductive schools of formal logic. This is where a lot of technical education fails students, as well as why ideas like constructionism and poststructuralism are important in seemingly clean/refined fields like engineering. An entrepreneur seeking to understand customer value (and their products proposition thereof) does not seek truth but meaning (what you might call a subjective truth or others a personal truth). Choosing to reject as 'nonsense' that thinking is really at the heart of our innovation problem more so than a lack of technical ability in the population. Market formation processes, Schumpeter's creative destruction, and Knightian uncertainty...find the truth in these explanations for real situations. They are abductive in nature and best treated through a non-positivist, non-modern point of view. But that is what we are talking about at the core, point of view.

Additionally, it is why diversity is so important...because that thing you call 'truth' is really a very personal rather than absolute thing except in the rare frames where it can be explicitly measured without affecting the result (and what does that sound like). Having the differing perspectives, points of view, and personal truths helps link customers and companies far better. [1]

[1] http://nature.berkeley.edu/er100/readings/Crewe_1997.pdf
Crewe, E. (1997). The silent traditions of developing cooks. Discourses of development: anthropological perspectives, Oxford: Berg, 62-77.