Tilde expansion in awk pipes

[limited time]

Hello, there seem to be some situations where tilde expansion does not work as 
usual.

BEGIN {
  "set -x ; echo ~'/path/to/file'" | getline output1
  "set -x ; echo ~''" | getline output2
  "set -x ; echo ~\"/path/to/file\"" | getline output3

  print output1
  print output2
  print output3
}

Running this script :-

❯ gawk -f script.awk
+ echo '~/path/to/file'
+ echo '~'
+ echo '~/path/to/file'
~/path/to/file
~
~/path/to/file

The set -x command turns on xtracing in zsh and it shows that awk is quoting 
the tilde sign.

All three forms work in the interactive shell :-

❯ echo ~'/path/to/file' ; echo ~'' ; echo ~"/path/to/file"
/Users/username/path/to/file
/Users/username
/Users/username/path/to/file

Is this by design ? The below three forms also work as usual :-

BEGIN {
  "set -x ; echo ~" | getline output1
  "set -x ; echo ~/'path/to/file'" | getline output2
  "set -x ; echo ~/\"path/to/file\"" | getline output3

  print output1
  print output2
  print output3
}

❯ gawk -f script.awk
+ echo /Users/username
+ echo /Users/username/path/to/file
+ echo /Users/username/path/to/file
/Users/username
/Users/username/path/to/file
/Users/username/path/to/file