On the other hand, figuring out what variables to control is huge part of science. Say the development of next generation DNA sequencing technologies. People tried a ton of different variables, conditions, reagents, flow cells, etc. And failed and failed. But eventually they controlled the right conditions, optimized the right things, and now the process is done in thousands of labs every day as a routine tool. This is a technology development example, but the same could be said of the conditions needed to make stem cells.
You use independent methods and good controls to deal with this. This is nothing new, it's been the basis of experimental science for decades. If you're allowed to publish without doing this, the field has failed. Molecular biology, in particular, has flourished because of the effectiveness of genetic controls. Mutants are highly reproducible (you just send out seed, cultures, or live specimens), verifiable (sequencing), and combinatoric (crossing).
If adding a variable changes the actually effect being estimated, then it may indeed have been worth adding.
If it doesn't, they'll just eat away at their precision.