[Question] why upload_only_when_tag forces stable branch?

[db4]

Environment Details

• Conan Package Tools Version: 0.35.1
• Conan version: conan 1.36.0
• Python version: python 3.8.10

Description of Problem, Request, or Question

I have a project with recipe and sources in the same repo. So I would like to upload conan packages for specific commits only. The only way to achieve that with conan package tools that I know is upload_only_when_stable/upload_only_when_tag. The former is not quite suitable as I need to upload testing channel packages as well. So I'm trying to go with upload_only_when_tag. But it surprisingly forces stable channel when used:

conan-package-tools/cpt/packager.py

Lines 777 to 780 in 7eff1ff

	if self.ci_manager.is_tag() and upload_when_tag:
	self.printer.print_message("Info",
	"Redefined channel by branch tag, "
	"setting CONAN_CHANNEL to '%s'" % stable_channel)

Why?