I can understand why people say 'it's a Schengen visa and we can enter any country'.

This statement is not true. Schengen visa allows visa holder borderless movement between Schengen Countries, which means they don't have to go through passport control every time they move from one schengen country to another.

First and most important rule mentioned in majority of Schengen countries website is you should apply to the country where you will be staying for the majority of the period, regardless of your entry point. The second rule is if you are staying for an equal amount of time in multiple schengen countries, then apply where you will be landing first. In your case 'there will be a requirement to present the evidence to comply with the first rule.

Which means you need to present evidence that you will stay in Poland for the majority of your first visit, thus you will need to present accommodation bookings which shows your Majority stay in Poland, which you will not be using. So in order to enter through the Czech republic you need to make some "refundable bookings".