Power creep is apparent in pretty much every type of coarse fishing rods. Back in the early nineties, when the bulk of the desirable Daiwa spliced tip rods were being made, most folks fished for barbel with a 1.25lb Avon rod and a heavy carp rod was 2.5lb TC. You are unlikely to find a barbel rod less than 1.75 and it's a struggle to find a full size carp rod under 2.75lb. Match rods were generally rated to little more than 4lb mainline (though 6lb never really bothered them anyway). These days, 2-8lb ratings are common, though how a float rod can genuinely cover that full range is beyond me. Poles in the early 90s were generally rated to a 14 elastic. Modern poles, even those that aren't especially powerful, are usually rated to 18/20+. Less powerful poles are still available but are generally seen as specialized tools.
Since the early 90s, commercial fisheries have come to prominence and the fish in them have got steadily larger. I remember fishing commies in the early nineties and them being dominated by pasty carp that rarely exceeded 3lb. Unless they've been recently stocked, the average carp on most commercials these days is way in excess of 3lb. Even F1s are regularly bigger. All of those changes have coincided with fewer people fishing rivers, especially with methods that would have been almost universal amongst river anglers of the 90s and further back.
Spliced tip rods, especially really light (actioned) ones appeal to an increasingly small number of people. That's the reason why so few manufacturers even bother. There's simply not the volume of sales there for them. If there really has been any power creep in the few current spliced tip rods still available (I'm not particularly convinced, the old rods were rarely as weedy as the ratings might suggest), then you can chalk that up to the pervading fashion for increasingly powerful rods right through coarse fishing.
I still have my 90s Daiwa Spliced Tip rods. I also have examples of two (of the three I'm aware of) current Spliced Tip rods. The way I use them, there's no huge difference in the power of the blanks. The most significant differences are in the weight, reel seats and rings.