@yoyoyaya I don't think the upgrades are as you say..'fixing flaws in the original design and engineering'. Instead, I think the upgrades are exactly that..upgrades. Brought about by evolution of the design and fresh thinking as time has gone by.
Any older product could be labeled as insufficient if compared to what has come since, and evolved. For just one example, one could say that cars from the past were flawed in their designs and engineering compared to today's vehicle...but i think that would be a disingenuous statement.