This is the internal circuitry of the common audio op-amp 5532 -
Fact is there are at least 2 amplifier stages from DAC to the line out already, and more if op-amps were used for this purpose.
The truth is that there is no issue with having multiple amp/op-amps "in the signal path". In fact some stages are essential and without them the signal quality worsens. Things only become a problem when additional non-required components worsen the performance in a particular scenario, but this can be said for just about everything, including capacitors and ferrite chokes and etc.
Double amping is appropriate in describing scenarios such as this example - you have a DAC with 0.001% distortion and a speaker amp with 0.01% distortion. You don't insert another speaker amp such that DAC(0.001%) -> amp(0.01%) -> amp(0.01%) -> speaker, as this will only worsen the performance for no reason.
However double amping should not be used to describe this:
Amp is bad and the DAC has an amp inside already (a.k.a. line driver or buffer), so connect DAC directly to speaker. You think that this case is obviously stupid. But think about whether the amp that is driving the line out is essential or not. (Hint: Minimizing cost is not the reason why that amp stage, if any, is there.)
With amplifiers it's always a tradeoff of multiple things - noise, distortion, output voltage, output current, cost. Which is why it is usually not recommended to use speaker amps (high output current, high noise) for line-level (low noise, low current). But what about a headphone amplifier that performs as well as a line driver when driving the same load? The two circuits are so similar that identical performance is not a thing of fiction. What if that headphone amplifier doubles as a line driver at the same time? Is putting an amp after it called double amping and is it bad? Think about it.
