I was not talking about my own recordings. I just do not record this way. I was talking about shows posted I listen to. You can always hear some reverb, or some slight misalignment and to each his own, but I think a deck designed to eliminate that problem is a better choice.
I didn't assume you were, and completely agree that best practice is recording all channels using the same clock. But sometimes doing that is either not possible or not practical, and in those situations the use of two non-clock-linked recorders can make for a recording of superior quality than choosing a less ideal location for the microphones just so a single multichannel recorder can be placed close enough to the board to also record a SBD feed.
The part I completely disagree is the statement that one "can always hear some reverb, or some slight misalignment"
in all recordings made from the combination of sources recorded on two non-clock-linked recorders, even when proper care has been taken to accurately sync the resulting files. If you hear that stuff, it means the files weren't accurately and correctly sync'd. It doesn't mean it's not possible to achieve.
Yes, such problems are quite common and quite possibly the rule rather than the exception for many posted shows made from a combination of files recorded using two non clock-linked recorders. But it by no means is a forgone conclusion that those faults are unavoidable in this day and age of commonly available advanced tools for the accurate manipulation and synchronization of the files. On the contrary, it's quite possible as long as one has the tools and is willing to make the effort to learn how to properly use them, and doing so today is much easier than it ever has been. Granted that not long ago this used to be considerably more difficult and was more error-prone, but software advances move quickly.
I have recorded this way many times, originally out of necessity, and still do at times for reasons of practicality even though I now have a number of multichannel recorders. It's not my prefered method as it requires additional work and careful attention to detail to avoid the problems you mention, but remains a valuable problem solving option. It's a trade-off which demands more work afterwards to achieve identical quality.