There are 3 different temp sensors..which one are you talking abouit??

The single and two wire ones have little tabs on the sides that you release as you stated, but if you squeeze too low , you are not releasing the tab..that is why they are easier to just pull off..but you can also use a small screwdriver to release each tab. Try that on the single wire one [ Temp gauge sensor] and once you have it off you will see he mechanics involved on the tabs
The Injection one should just pull off ..it just has a ring clip that snaps on.