That has always struck me as a sensible transportation plan for a family.
1. It's simpler than a normal hybrid ICE/EV in that a BEV/HEVV is all electric with two power sources (battery and hydrogen). If I'm right that a ICE/EV hybrid has extra potential for mechanical failure (either the ICE engine goes bad or the electric motor goes bad), having just one motor type in a hybrid ICE/EV simplifies things to have less that can go wrong.
2. Hydrogen refueling is practically non-existent. Battery charging seems more common and easier to find on trips, and is easy-breezy to charge at home (if you own your home). So if you can get most of your miles from the battery it's the easiest way to drive (even easier than an ICE car in that an ICE car requires me to stop every now and then to fill up even for local driving, while a BEV requires none of my personal time for local driving since I plug it in at home and ignore it while it charges).
3. Adding a hydrogen tank to a car with a fuel cell adds a lot more miles per weight than adding more battery. My EV gets 200 miles highway driving with the battery capacity it has (which is fine with my wife wanting to stop every 200 miles anyway LOL). A BEV designer using mine as a model would have to make the battery twice as heavy to get 400 miles with the highway speed I like drive. But a BEV/HEV hybrid could add those extra miles with relatively light hydrogen.
4. Hydrogen is more costly to produce than battery charging. It's more costly also than producing gasoline (thus it'd be an argument for driving an ICE instead of hydrogen car). That is, except for one very important thing to those of us who live in the south and own our own home. My solar system that does most of my EV charging for free (as well as powering my now all-electric home mostly free) could also run a hydrogen producing electrolyzer on days I have a fully charged EV and home batteries with no other place for my excess solar to be utilized. The efficiency of an electrolyzer is bad (at best 70% power retained after doing the round trip of using power to produce hydrogen, then later using the hydrogen to create power). So I'd produce hydrogen only when I've exceeded all else I can do with solar. But it could be stored up over time for the next long trip.