Bull Puts — should IVR always be above 50?

I am new to options and from videos I understand that you should look to sell if IVR is over 50 and buy if under 30.

The platform I use is Tasty Trades and they have a page to follow other Tasty traders and you can filter a specific strategy which I choose Bull Put Spreads. I noticed on the page that all the IVR was under 30.

Are they looking at IV or just based on their own bias? What are the main things people look at before doing a Bull Put Spread?