Autoptimize Pro has “Boosters” to delay JavaScript (esp. interesting for external resources), CSS and HTML (which can be very impactful for long and/ or complex pages). Up until today’s release the delay was either until user interaction OR a set timeout of 5 seconds, but now you can choose the delay time yourself, setting it to e.g. 20s or 3s or -and that’s where things get a teeny bit shady- 0s to disable the time-out, waiting for user-interaction to load the delayed resources.
Setting the delay to 0 is a bit shady because at that point you are hiding those assets for performance tests which -although artificial- is likely to improve (lab test) performance scores. If you do use the 0s delay then do take into account that *real* users will still need to load/ render those assets and that that still may be a sub-optimal experience.