Where is your metric? By how much will you be declared more productive? Is it just time to achieve a result? Because that is obviously wrong. How are you accounting for quality, or even measuring that X? Do you account for readability? maintenance? documentation? factoring? over-engineering?

There are so many visible as well as hidden factors that attempting to measure any (let alone all) of that is a pipe dream.

Also, by writing the second one you are not accounting for second version effects since it is a reimplementation of something you know, and if someone else develops it for you then you just changed a major variable.

I get that you said "oversimplified", but this is just like saying "thought experiment", yet as soon as you confront that to the real world, it just doesn't realistically fly.