TL;DR

Glazed terracotta (and some other blocks) get placed backwards from how they look in the hand. It makes it unintuitive to place.

(arrow points backwards in hand but forwards in world, opposite of blocks like furnaces)

Background

Various blocks can be placed in multiple orientations based on the player's rotation (chests, pistons, etc). For most of these blocks, the side that will be facing the player when placed is positioned like so:

• Facing towards the player in first-person
• Facing away from the player (on the inner side) in third-person
• On the right half of the GUI icon
• Facing straight out in an item frame
  This is illustrated in the following two images:
  
  

The bug

Some blocks do not follow this convention for one or more models, resulting in unintuitive or confusing placement.

= matches most blocks
= affected by this issue
First person is most relevant since it defines your intuition for block placement, but I've included blocks that are unusual in third person for the sake of completeness.

Block	First Person	GUI	Third Person
Glazed terracotta	180°	180°	180°
Observer (see note*)	90°	180°	180°
Piston/sticky piston (probably WAI)
Fence gate
End portal frame	90°
Banner	90°
Command block	90°
Chiseled bookshelf	90°
Stonecutter	90°
Trapdoor	90°
Button	90°
Stairs
Skull
Chests
Anvil
Big Dripleaf
Small Dripleaf
Decorated Pot
Calibrated Sculk Sensor
Grindstone
Crafter
Vault

Attached are images of affected blocks in the contexts in which they appear inconsistent, with a before ("Vanilla") and after ("Fixed") image.

(* Rotating the observer in the GUI makes it look rather strange, so a more correct fix may be to alter its placement so that the "face" faces the player when placed instead of the back.)

One more thing
Blocks that "attach" to the face you click on (logs, shulker boxes...) follow a convention where the model is oriented vertically. However, jigsaw blocks do not follow this convention and are also confusing to place.