The local coordinate caret notation when directed forward will select the block forwards from your feet instead of your crosshair.

Steps to reproduce:

Set up a platform and reference blocks in front of you

Look at the block directly in front of you

Run /setblock ^^~2 glass (or any block)

The video attached may help with this

Observed result:

The block placed is in front of your feet instead of your crosshair

Expected result:

The block placed is in front of your crosshair

Note: The video size is too big so here is a link to it: 

https://share.icloud.com/photos/042c_J51kKQa-tgbK_bDs2tKQ