Freestyle rappers are something else.

Some (or most) come up with and memorise a huge repertoire of bars for every word they think they might have to rap with and mix and match them on the fly as they spit

Your example above is called a “filler” though, whip is essentially a placeholder they’ll often inject while they think of the next bar to give themselves a breather (still an insane skill to do all that thinking while reciting something else, but they can and do)

Example:

• My name is M.C. Squared and… [I’m here to make you scared | my bars go over your head ]
• You think you’re on my level… [ but my skills can’t be compared | let me educate you instead ]m

The combination of fillers is like playing with linguistic Lego.