Is not needed xcodeOrgId and xcodeSigningId in iOS device test?

Hello, I am testing iOS real device using WebDriverAgent.
I want to install tested app using WebDriverAgent and then to start test. But there is a provisionong profile issues. So I decide that test for already installed app.
(My WebDriverAgent is already Signed)

I don’t know why installed app is working well. But It working good.

In this situation, when I make a session between real device and appium server, xCodeOrgId and xCodeSigningId is not necessary.

I can make connection with platformname, devicename, udid, platformversion, app.

My questions are

  1. Why can an existing application be replaced with an ipa file without installing the application?
  2. In this situation, are xcodeSigningId, xcodeOrgId not necessary right?

My writing might be weird because I’m not good at English, but thank you for reading it until the end!