Musk really DOES mean the same rocket (first stage) launched in a 24 hour period. See this article:
https://spacenews.com/spacex-target...-in-2019-full-reusability-still-in-the-works/
Considering that it takes DAYS between a static fire test, rollback "just" to add the payload and roll it back out for launch, there's massive amounts of changes they need to make in the next 1.6 years. And I'm leaving out the other things I already mentioned before about the steps between landing from flight 1 and launch of flight 2.
Also it assumes no cheating such as flight 2 not having a real payload aboard, or as a stunt just flying the booster with no 2nd stage.
Another issue they would normally have to deal with is pad damage. But they can "cheat" that by launching from LC-40 for flight 1, then after taking the landed booster to the HIF at 39A, launch from Pad 39A for flight #2. This means of course both pads would be out of operation for awhile after (and no flights on both pads for maybe 10-14 days prior to allow for repair/refurb time on the pads).
I'd be more impressed to see them launch 4 different rockets at the Cape in 5 days (2 rockets per pad, 4 to 5 days after the first one launched). THAT would mean something they could probably routinely do for launch cadence (inventory permitting), rather than some special case.
Now if Musk wasn't talking about "BFR" to replace Falcon-9 in 5 years (yeah, right), then sure I'd expect after several years SpaceX could add the infrastructure and procedures to routinely launch a rocket twice in 24 hours. However, I expect real-world that Falcon-9 will be launching payloads for the next 10 years, and beyond. And that assumes that BFR really does work, eventually. But that upper stage (BFS) has so many unknowns about it, that it's going to make Falcon-Heavy's long delayed timetable look "fast". Which is why they are going to build and test a prototype of the upper stage FIRST, since the first stage will be relatively simple to do by comparison (I said relatively).
Meanwhile though, Musk is publicly saying that BFR will replace F-9 relatively soon, in which case despite likely reality for BFR probably taking way way longer (Falcon Heavy), I wonder if they'll devote the $$$$$ to upgrade the ground logistics enough to really truly do a fast turnaround launch of Falcon-9 boosters on a regular basis.