I would have thought that it'd be the opposite i.e. they start out with a bigger and better quality board and then save money by redesigning it smaller and cheaper
They started out with the smaller cheaper board because it was smaller and cheaper and they THOUGHT it would be ok, which it turned out not to be. My very early mmt8 board is almost cottage industry made - that thin, almost-see-through fibreglass PC board with copper tracks that you can get from Rat Shack as a blank and etch yourself...
They did the new board because of all the factory recalls and customer complaints about faulty buttons on both the HR16 and MMT8. Since they already had a business product lifetime schedule planned for X amount of years for this product to bring in Y amount of income, they had to continue with the improved product or else stray from the business plan timeline and so lose even more money. The SR16 would have also been a part of this plan and so was meant to fit in as the successor at a certain time Z of the timeline and not before or after, to maximise profit. A tricky business, "business".
The thing that is also of interest is that at that time Alesis were one of the first electronic instrument companies to pioneer the whole automated integrated board and components manufacturing method. I have an Alesis 1622 mixer of that same era - all the knobs and sliders are actually just carbon tracks on a big PC board, and the actual plastic knob or slider has on its underside the electrical contact for the carbon track. So there are no real potentiometers in it. It's all made on a PC board. Which then lends itself perfectly to cheap robotic production line manufacturing, which made it by far the cheapest and highest spec 16 channel mixer of its day. Too bad 20 years later that the carbon tracks are wearing out on it now and I can't just pull out a slider pot and replace it. Nowadays many of the companies like Behringer have made this sort of manufacturing practice commonplace. They don't fix warranty jobs - they just give you a new one because it cost them so little to make its cheaper than fixing them. And the customer now does the Quality Control which used to be part of the manufacturing process, in order to bring the sales price down on the item.
Cheers, graham