This answer describes the behavior of 3.3.4 (and 3.3.8) for Windows 32-bit, which seems to automatically report folder results as if I'd opened each file, as long as I have my session settings correct.
To perform a comparison that ignores unimportant differences, it is necessary to compare the file contents. BC3 can't know if line endings are the only difference (for example) unless it scans the contents for line endings. Therefore, you must set the "Compare contents" checkbox under the "Requires opening files" section. By doing so, the folder comparison automatically scans all file contents, I don't have to open each one individually.
A "quick test", by definition, is based solely on directory information like timestamp and size. It is quick because it does not open nor read the files; so if quickness is what you desire in a comparison, it cannot be rules-based. The concepts are incompatible.
You can see whether a "quick" or "contents" comparison has been run for any pair of files in a folder-compare window by looking at the middle column. If it is blank, only a quick test has been run; if there is an icon, a contents test has also been run.
That icon will be a black ≈
("almost equal") symbol, two wavy lines, when a "Rules-based comparison" has detected only unimportant differences. The files themselves will be black and treated as matching if you have "View > Ignore Unimportant Differences"
active, otherwise they'll be red or gray and treated as mismatching.
For the meaning of each possible icon, here is the relevant section from the Beyond Compare 3 help file:
Folder Compare > Understanding the Display">