I totally believe that. Many of the guest hosts were in the TV news business, and most of them host daily programs. That's not a situation where you can just schedule everything around Jeopardy! and block-tape your own work at another time. WWtBaM and the Today show gave Meredith Vieira every possible accommodation, yet the game show still had to have a few fill-ins nearly every season.
And that's when the Today show and WWtBaM were produced only about a dozen blocks from each other. You really think Anderson Cooper or Robin Roberts are going to fly from NY to LA and back to do 230 episodes of J! every year? Between taping and travel, that would eat up four days of their week, two or three weeks a month for about eight months of the year. There's just no way.
There are some game shows whose production has been built around the host's schedule... Pyramid with Dick Clark, and most notably Family Feud with Steve Harvey. Wheel of Fortune might be able to do it one day. But that's not practical for Jeopardy! They have to create 740 clues for every taping week, each of which must be meticulously fact-checked. They can't just cram a few shows' worth of material at the last second because of scheduling issues with an actor or journalist who is the daily host.
And unlike most other game shows, J! has returning champions who are cast from around the country. It would be very difficult to consistently bring returning champions back on short notice. What would the host say? "Matt isn't able to join us today to defend his championship because I just got cast in a movie that shoots next month, and we had to reschedule three weeks of tapings, and that didn't give Matt enough lead time to travel back... so here we are."
I'm not sure how much Alex himself was involved in writing the clues, but Jeopardy! obviously has always had a full-time staff devoted to clue writing. I do recall reading that Alex had the final say in determining whether a response was correct or not, but I'm guessing that authority was given to him only because he had been at Jeopardy! for many years. Since Mike is also the EP, it's a safe bet that he'll now have the final say when such disputes arise, not only on the shows he hosts, but also on the episodes hosted by Mayim.
I've tried to be fair in my analysis of the hosting selection process, and the fact that Mike was essentially the only candidate with the authority to settle contestants' objections was certainly a factor favorable to him. More broadly speaking, the selection of Richards means that Sony gets to save costs by having the same individual serve as EP and host.
I will have to respectfully disagree with your analysis about a potential heavy burden arising as it relates to clue writing. Even if Jeopardy! selected a host who lived in the NY area, I would figure that the show's full-time, behind-the-scenes staff would still have plenty of time to write and fact-check clues far in advance of tapings. If the host had to be an integral part of this process, then he or she could do this portion of the job remotely.
Match Game in the 70's did it too I think you could say, given Gene Rayburn would fly out from New York what twice a month to record 10 to 12 shows depending on the time period between daytime and nighttime shows over a weekend? And they had no summer break at least in the 7x era, so they were doing some 250/260 new shows a year. But that too woulda been much easier to pull off than Jeopardy would be for sure, even with the addition of needing 12 celebrities all told for use on both days of taping.
If I'm not mistaken, I believe that Gene Rayburn lived in Cape Cod, Massachusetts instead of New York during the 1970s. However, I did not know that that many shows of Match Game were produced each year back then, so I appreciate that bit of information.
While candidates residing in the Los Angeles area no doubt had an advantage in the hosting selection process, it would not have been an insurmountable obstacle for an East Coast-based individual to fly to LA every three or four weeks or so and then spend three or four days taping five episodes a day. And I'm honestly not sure if the logistics of bringing back returning champions (in such a scenario) would be materially more difficult than the issues Match Game faced in recruiting and retaining celebrities.