Unknown freezer parts do not correspond to assembly diagram

The evap coils in my freezer have been building up ice, so I opened up the freezer to diagnose the issue, and was confused by what I saw:

My fridge is the following model (freezer assembly is shown at the attached link): HTS22GBPBRCC

I’ve discovered that the white probe at the bottom of the copper pipe is a temperature sensor, but I have no idea what the blue object is. My guess is that it’s the defrost thermostat since it’s clipped to the copper pipe, but it doesn’t look like any defrost thermostat I’ve been able to find, and it’s definitely not the thermostat that’s supposed to be in my freezer. Moreover, there shouldn’t be a temperature sensor in my freezer either, at least according to the freezer assembly.

According to the freezer assembly, my freezer should have two separate defrost thermostats:

1. Thermostat 1
2. Thermostat 2

My questions are as follows:

1.) Has anyone seen this blue part before? What is it? If it’s a defrost thermostat, it doesn’t appear to be wired like the correct defrost thermostat for my freezer.

2.) The freezer assembly states that I should have two defrost thermostats – is that unusual?