In previous versions, running delta --version would output the version number directly to stdout:

$ ./delta-0.17.0-x86_64-unknown-linux-musl/delta --version
delta 0.17.0
$ 

In delta v0.18.0, this invokes the pager and pipes the output through that. The pager will then most likely quit immediately (because there is less than a page full of text to display). However this can still be noticeable, depending on the settings of your pager. For instance, with the environment variable LESS=-c, less will repaint the entire screen, even if there is only a single line of output. It ends up looking like this:

$ LESS=-c ./delta-0.18.0-x86_64-unknown-linux-musl/delta --version
delta 0.18.0
~
~
~
~
~
~
~
$ 

I would expect that a request like --version would not invoke the pager and would not fill the screen with tildes.