I have a vague sense I haven't really answered your question somehow.

You have done something better; you have given me things to think about. Thanks!

Not only is the freezing water assertion testable,

I am going to risk being a bit obtuse and pedantic here and ask if you are sure. That is, can you establish that the statement "Water freezes at 32 degrees Fahrenheit" is true or false? Suppose I ask you to prove it to me?

You will probably start with a thermometer. Okay, the most expensive thermometer for sale on Amazon costs over a thousand dollars and is accurate to only ±2°C. So we will have to be very specific about equipment. And even if we get better tools, there will still be a limit to the accuracy of our measurement.

Next, you will want to specify a very precise environment. Air pressure plays a role and the container makes a difference. And of course, you will want to obtain the purest water possible, but even the highest standards allow some contamination.

Suppose we have a laboratory kept as close to 32 degrees Fahrenheit as possible. Into this lab we introduce a block of ice which is also at 32 degrees Fahrenheit (or just a little colder), and a beaker of water which is at 32 degrees Fahrenheit (or just a little warmer). What will happen? I don't know! If the water doesn't freeze, doesn't that disprove the assertion?

In the end, I think the best you can hope for is a highly qualified claim like "Nearly pure water, when cooled from 34 degrees Fahrenheit to 30 degrees Fahrenheit, freezes at approximately 32 degrees under typical conditions" which adds to our understanding of the world but is not an elegant and universal truth statement.

That kind of statement does not sound so different to me than a claim like "In modern democratic capitalist societies, minimum wage laws as typically drafted and enforced generate more benefit than harm to low-skilled workers." I am not even sure which would be easier to test; it all depends on your criteria.

it's also a matter in which almost no one has an emotional stake.

This is highly significant, but of course has nothing to do with the truth value of the assertion, and everything to do with the irrational kind of shortcuts that helped our ancestors make babies instead of wasting time worrying about nucleation sites.