It's a new system. The Navy "spreads out risk" by spreading out the installation of new systems through many ships. They've enough Burke hulls that they have this luxury. You'll recall that one major criticism of the Ford was that it jammed some 23 new systems onto one hull, causing massive "teething troubles." However, the flip side is that we build about a carrier every 10 (or more) years. One new system per hull then would be 230 years to try those 23 systems out that way. Destroyers are a different animal. Put only one new system on any given hull. If it fails, pull it off, and both the ship and the class don't particularly suffer. The first (and immediate subsequent) Flight IIIs are already introducing SPY-6, and any teething issues are worked through. As noted, SPQ-9B was already proven on multiple other hulls beforehand. This new jamming system is introduced and proven out this way. As these all become proven and "standard" they're then "amalgamated" onto the rest of the fleet at routine maintenance sessions. The schedule Jack Lucas was on, and the schedule the AN/SLQ-32(V)7 was on, both were too new to have together on Lucas when she first came out.

Another feature of Navy upgrades is that you'll find they insist on backfitting new systems onto oldest ships coming in for maintenace, and literally working their way forward to the newer ships in chronological order as they each come into the yard. Thus, SPQ-9B began appearing on about DDG-79, and then worked up through DDG-80, 81, etc. However, it was successful enough that a decision was made to "jump," and now it also is being installed from DDG-119 forward as well. That's a bit unusual, but it seems to be a "good system." So, you'll see the system get added with time to the ships before DDG-119, but also find it on all new builds.

After WWII, we had a huge surplus of hulls, many in mothballs. It was then easy to "grab" a hull and stick some new system on it and test it out, while new construction was uninvolved. We no longer have that luxury, nor yard capability, etc. New tech frequently has to be tried out on production and in service vessels. This is how the Navy handles that; backfitting older ships first. With the carrier catapult, arrestor, elevator, propulsion, etc. systems, those weren't "backfittable." The new EMALS, etc. needed the new power system and hull design. So, that had to be done, altogether. (Chorus: "That had to be done"...) (See the movie "Airplane!"...) Otherwise, spreading out technology risk as much as possible is sound policy, and the Navy has done that as much as it can for a long time.

Here's another example. Notice how this new gun was first fitted to DDG-89. If you then choose to follow it, you should see this pattern emerge:

https://www.navsea.navy.mil/Media/News/Article-View/Article/4398950/nswcdd-delivers-next-generation-mk-38-defense-system/