So you said "not true" then agreed with me? Just because you hear party's voice on a reference track it doesn't mean he wrote that whole reference track. That's the only point I'm making.
I broke down how song writing works, particularly when they're collaborative. Your last sentence "I don't know if Drake does that" shows that you agree with me. We don't know how much writing he puts into his own songs but people here think if they hear a reference track that it means Party wrote it all then sent it over like "hear record this, it'll be a hit." No. Most times there's a pre existing structure and framework (either from party, drake, or another writer altogether) and it goes through various evolutions before it makes it to an album. Party's reference track that you're now hearing might be the third or fourth version of that. There could be scratch tracks drake recorded before party even ever heard the song. Party could have taken a rough version drake sent over for more work and then changed lines or a flow and sent it back.
That's the point.
And I don't understand the distinction you're making with Jay-Z. So what if he wrote it. There's recordings of other rappers and producers saying HIS bars in a way they think would sound better. Again, that's the point.