While that's true to some extent, it doesn't mean that knowledge shouldn't be preserved in a format that would be accessible by a recovering civilization. Just because they don't have electricity now, doesn't mean they never will, and a handy guidebook telling them how those things work will speed things up later.
It does mean though, that the information should be prioritized - there's a T-shirt/poster floating around the internet full of "things to take credit for discovering if you go back in time". Most of the items it lists are either critical discoveries that led directly to improvements in quality of life, or were the basis for other technologies. Pasteurization, antibiotics, electric generation, radio, flight, and more. (It's
here by the way.)
A guide like that is a good start - build things up in stages, add in more (useful) detail, never assuming that the reader will already have a tool unless it has already been explained how to make it. Then if you want to go hog-wild, after you've reached the part explaining how to make a computer and digitize information, put the stuff that would require a heavily industrialized civilization into a digitized code format and explain how it's encoded, so they can read it when they're ready/able to use it.
Random data being used for research though, is likely totally useless. Not only is the DNA/RNA sequence from that rat likely to be useless to a recovering civilization, depending on what sort of cataclysm happened, the DNA/RNA of a rat may not even match what was recorded. Leave stuff like that to DNA/Seed banks, unless it's part of an explanation of "what DNA/RNA is", and even then, the whole set is pointless. (Also probably patented.) A Tokamak reactor may not be useful to a low tech civilization, but with the boost provided by being taught how to make hydro-electric generators, lights, heaters, radios, and internal combustion engines (they can run on cheaply made alcohol, they're just less efficient that way, and wear out faster.), they might be able to make use of that information in only a few generations.
The real problem of course, is format, and ensuring that not only does the information survive, but that these future people are able to understand it when they do see it, rather than thinking "Oh, pretty metal plates with squiggles on them. I bet I could melt those down and make a great set of knives out of them."