M3 Ultra makes no sense. The M3 family was obsoleted with the launch of the M4, many months ago. Zero reason to release an M3 Ultra at this point.
M3 isn't obsolete. Apple is today releasing a iPad Air with an M3... how is it obsolete when it is in a new product? It is not a maximum bragging rights option , but obsolete (no support , won't get software updates) ... nope.
It makes sense if Apple is trying to squeeze more revenues out of the R&D development costs for the M3 Max. The M3 Max only ran for a year in the MBP 14/16". And then it gets to go where? Apple develops this substantively large chip and then throws it away after 12 months?
Nobody does that for relatively large dies. Nvidia came out with their new data center chips but didn't stop selling the old ones.
Similar reason why the Mac Studio and Mac Pro floating on for extended period of time after MBP 14/16" jumped off the M2 ... somewhere for maximum sized M2 dies to go to recoup more of the investment.
It would be awkward. But it does make some sense if trying to save money on chip costs. ( and if Apple has more N3B wafers to soak up on their TSMC contract. ) . The M4 Max is typically no where near 2x as fast as a M3 Max. The M1 and M2 has large gaps but the M4 is better , but not by a HUGE amount. Twice as many CPUs/GPUs/NPUs/video encode/decode the M3 would have an advantage for folks who mainly needed highly parallelized , larger workloads.
If the M3 Ultra was 'brand new" die like suggested, then no. It doesn't make much sense. That single die solution from "Max Tech"... that is worse than Gurman as far as accuracy goes. Only if the production costs were vastly cheaper than two dies and Apple could substantive lower the Ultra Studio costs. I doubt that is true (but depends upon the costs of InFo-LSI packaging costs and defect overhead. )
And as mentioned if delay a Mac Pro to Fall and roll out M4 Ultra on that they'll have the product gap between two products folks have grumbled about. When Studio gets M5 Max / M4 Ultra the Mac Pro goes M5 Ultra . Rinse and repeat .