No "waiting for data" message when using F command on a pipe

[gwsw]

Steps to reproduce:

1. Run i=0; while :; do echo $i; let i=$i+1; sleep .2; done > file &.
2. Run less file.
3. Type F.
4. Note that a "Waiting for data" message appears while content is scrolling.
5. Exit less.
6. Run i=0; while :; do echo $i; let i=$i+1; sleep .2; done | less.
7. Type F.

Expected behavior: A "Waiting for data" message should appears as in the case of viewing a regular file.

Actual behavior: No "Waiting for data" message is visible.