com.apple.quarantine attribute does not cause any warnings I've read in several places I've found via search that quarantine flag results in a warning when app is tried to be run (and then flag is cleared):
https://superuser.com/questions/28384/what-should-i-do-about-com-apple-quarantine


  it can ask for user confirmation the first time the downloaded program
  is run, to help stop malware. Upon confirmation the attribute should
  be removed automatically, and then the program will run normally.


What causes OS X to mark a folder as Quarantined?


  When the Launch Services API is used to open a quarantined file and
  the file appears to be an application, script, or other executable
  file type, Launch Services will display an alert to confirm the user
  understands the file is some kind of application.


However on my MacBook (MacOS Mojave):

xattr -l /Applications/Docker.app/Contents/Resources/bin/docker
com.apple.quarantine: 01c1;5d958e46;Chrome;D01EADC9-90F1-4DAB-81A0-A96722A65A11


but I can run that app in command line with /Applications/Docker.app/Contents/Resources/bin/docker and it works w/out warning. I also start Docker.app via Command-Space without warning now, but 

xattr -l /Applications/Docker.app
com.apple.quarantine: 01c1;5d958e46;Chrome;D01EADC9-90F1-4DAB-81A0-A96722A65A11


Why I have com.apple.quarantine attribute (not cleared already) but it has apparently no effect?
Special attributes cleared when I finished install of new version of docker desktop (I stumbled upon the @ in ls -l output when new version was being downloaded). Apparently during download and install some tech details were under the hood and I did not guess they effected main/active file attributes.