Do you think you could get away with not being in the US when the US spouse submits the Visa?
Of course you can.
It's perfectly fine not to enter the UK together, as long as you are already in the UK. What you can't do is return to the UK AFTER your wife enters on a spousal visa (because you either have to be travelling with her, or before her).
The visa category is 'Overseas Sponsor Returning to the UK', not 'Overseas Sponsor is Entering the UK at Exactly the Same Time as the Applicant'.
All it means is that you have been living abroad and are now returning to live and work in the UK, and are applying for your spouse to join you in the UK.
It doesn't mean that you have to travel together.
To avoid fraud they would have to answer correctly and say you were in the UK at the time of applying.
With that answer it would also mean they would then have to check that you're not travelling with them.
It's not fraud - she puts on the visa application exactly where you are on the date she applies for the visa. If you are in the US, she puts 'US', if you are in the UK, she puts 'UK'.
It makes no difference, because as I said above, there's nothing in the visa rules that says you have to travel together, or that you have to be in the US when she applies.
The next question in the list would be answered "you're not living in the UK"..because if you answer yes here then surely you become a "6 month payslip case"? Or maybe they have a grace period...either way, I imagine that would then cause confusion to the officer processing your case. So perhaps in the notes section it could be explained that the UK citizen left for a job interview, got the job and intends to stay present in the UK until work starts. It seems crazy to waste $2,000 on flying back to the US for what could be less than a week.
Well, this is what we are not sure of: whether or not you would become a '6-month payslip case or not'.
If you are returning to the UK for a job, it says that you don't have to have started work in the UK, but you do have to have a confirmed job offer starting within 3 months.
It also says that the £18,600 earned in the previous 12 months can be from foreign or UK income. This implies that you can start the job in the UK, and use the US income from the previous 12 months, to meet the requirement. Therefore, this implies that you can still apply under Category B: 'Less than 6 months with employer - sponsor returning to the UK', if you have already started working.
What is DOESN'T specify though, is a case study where someone has already started working in the UK and still applies as a 'sponsor returning to the UK'. So we don't know for sure if this is acceptable or not.
The member that KFDancer mentions above got her application in just before her spouse started his UK job. He was in the UK when she applied. He started work in the UK before her visa was actually processed. Her visa was granted with no issues.
There is another member here who is in the situation that her husband will move back to the UK ahead of her and work for a couple of months, before she applies for her visa. I believe she is going to try to apply under Category B: 'Less than 6 months with employer - sponsor returning to the UK' and see what happens. If her application is successful, we will have an example of it being sufficient for the visa. If not, we will know for sure that you can't do it that way.