Perhaps you have a different idea what a significant digit is? (I assume you are American)
First of all: before the decimal point, all digits are significant. Ooops.
Then lets look at this:
19000K converted to Fahrenheit: 33740 F
So, you want to adjust this for "your significant digits", and cut it to 33000F.
Now, we "lost" 740F ....
Which translates back to: roughly 200K ... so let me check my calculator. It seems to be 190K. (Nice coincident, see below)
So: because of "your idea of significant digits" you want to lose 190K, in a unit conversion. Well, that explains Mars lander crashes.
Looking at the coincidental loss of 190K by "your conversion" to F, we talk about 1 percent
You want to lose 1% precision/information by converting to another unit? Because of: what exactly?
The measurements in the original article averaged/settled around "19000K plus/minus 4000K"
That is not a margin of error, but the range of measurements.
This is the logarithm of 7/3 (picked it as 7 and 3 are primes): 0.3679_7666
0.3679 I calculated by hand. The _ is the marker for "significant digits".
The 7666 after the _ marker: is a guestimate. Which is close enough for any real world applications, like finding your "exact" position on the globe by triangulating 4 stars in the sky. So the significant digits are: "0.3679" because they are a real confirmed part of log(7/3) and because I indicated with the "_" (and explained so) that the digits behind are not "significant" as I guessed them.
It is perhaps not good enough to land a probe on Mars, though.
Point is: Converting 19000K plus/minus 4000K translates to Fahrenheit as 33740 plus/minus 6740.33 (yes, for nitpicking purpose I did not round it) has absolutely nothing to do with significant figures.
Rot learning for your exam, is not the same as understanding.
Sorry: but do you really have "significant digits" before a decimal point in your country? Then I feel sad for your education ... as that makes no sense at all.
You lose 1% of accuracy by converting to another unit, and you find that: okay! ... as an engineer? You are working for Boing, right?
Of course, if you do not like my logarithm above, we could follow your "zero schema" and write it as " 0.36790000" into your log table. Then: my guestimate about the other 4 digits, is lost. And that increases your problem of landing a probe on Mars.
So, no damn idea why you insist a conversion from a scientific unit into another one has to lose 1% "precision" or "information" because of "significant digits".
That is simply not what "significant" means. I owe you $4444? No problem, I just transfer $4000. Or I just transfer $5000 ... hm, I have to think about that. Keeping your "error margins" transferring $4888 is cheaper for me and makes you hopefully more happy? Strange: 4444 was significant. And if it was 4400 and I convert it to the current currency exchange from Thai Bath to dollar, it would be: 144,121.14 THB versus 142,694.20 THB. That is a one month rent difference in SIGNIFICANT, for a simple apartment in Bangkok.
Anyway, if I have to rely on a payment then I need to pay my rent, I rather have it either paid "exactly" or rounded up, and not cut into: significant digits :P