The problem isn't the number, it's the schedule. The Type 26 won't be in the water before a decision on the Sea 5000 frigate is made. In fact, the design may not even be frozen by then. It will,be hard to argue it is a MOTS solution if it's still just a bunch of drawings.
True, don't want a repeat of the MRH90 or ARH. That said in hindsight the Type 45, for example, was a vastly superior platform to the F-104 (even the considerably updated F-105) that missed serious consideration as it was seen as too developmental.
What has been seen in reality is that the Darings are a generation ahead and are larger, faster, longer ranged, more economical, have much larger power generation capacity, better damage control, than the F-105, let alone the F-104 baseline. Due to their more modern design and power systems they ironically would likely have been much easier to fit the AEGIS Baseline 7.1 and AN/SPY-1D(V) to than the already tight F-100 has proved to be.
All six Darings were in service before Hobart hit the water and four of them were in service before F-105. The Type 45 had problems associated with the UKs own shipbuilding cutbacks but they were sorted well before those of F-105 building efficiency of which actually went backwards compared to the first four (due to design changes, obsolescence and supply chain issues).
Even discounting the Type 45 due to the lack of an existing AEGIS version you can compare the German and Dutch, or even the Japanese and South Korean AWD projects, let alone to a minimum change Flight IIA Arleigh Burke to the Spanish design selected as the basis of SEA 4000 and there is the frightening, but still likely possibility that they could have been built more easily and less expensively, in less time than the F-100.
All hindsight but realistically nothing that a thorough, properly scoped, risk assessment couldn't have identified. The unknown quantity was Navantia's complete lack of experience in supporting an overseas licence build which has to share top billing with the late 90s, early 2000s Australian shipbuilding black hole (not to mention government over optimism in how hard and expensive it would be to rebuild the capability) as the root cause for cost and schedule issues.
What does this have to do with Type 26, easy, like the Type 45 the Type 26 will be a vastly more capable and versatile platform than most of its competitors, its design and build strategies will be far more compatible with export and overseas build than most of its competitors and like other recent UK designs it will have been designed and reviewed to death before steel is cut.