No, that makes no sense. Apple gives people very specific levels to signify their job function and responsibility. If your dad got replaced by a kid, most likely that kid had the same ability to perform the job as your dad (in which case it's likely your dad was underperforming because it would've been more expensive to replace him if he had been performing fine)

The current knowledge facet does not come into play so much as performance does. It's entirely possible your dad's lack of current knowledge made him an underperformer, in which case I think that's a completely reasonable replacement. Albeit unfortunate for your father given the nature of technology and the pressure it imposes on people in the career even those with families. But there is nothing sinister about replacing an underperformer with one who will not underperform, and it certainly has nothing to do with your dad's age or "hunger to work."