Why does the value of %posttrans comes as 0 after installing any package?

Issue

• While installing any rpm, the argument to %posttrans should be equal to 1; in RHEL 7, it is coming as zero (0)

  # rpm -ivh /var/tmp/foo-0.1-1.noarch.rpm
  Preparing...                          ################################# [100%]
  Updating / installing...
     1:foo-0.1-1                        ################################# [100%]
  arg 1 = 0
  

• However, on RHEL 8 and later it gets arg 1 = 1 correctly. The same is documented in Upstream Fedora project.