Yes, PRNGs are not entropy sources and using a PRNG does not generate new entropy. But using a PRNG also doesn't reduce the entropy it already has. You only lose entropy by transmitting information, and the entropy lost is equal to the information transmitted.
For example, if an adversary with perfect analytical ability learns the outcome of a simulated dice roll you performed using /dev/random, they gain log₂(6) bits of information and you lose the same amount of entropy, irrespective of how many bits you actually read from /dev/random.
You have made assumptions that I did not, and you're talking past me (at length). I didn't say anything about sticking a PRNG between Lemire and the entropy source.
If I'm generating an RSA key pair I'm going to pull kilobytes of data from the entropy source, not a PRNG, and that data volume will be a fixed multiple of some word size that means that every bit I take has a purpose.
If I need a non-multiple of the word length worth of entropy from the entropy source, no standard library I know of handles that. C, Java, a few others always fetch 32 or 64 bits of data and then throw most of it away, even if the system call might allow finer increments.
If I need 6 bits or 200 bits, I have to stick a CSPRNG in there or throw entropy away. If I do the latter (which people often do by default) I'm robbing bits/second of entropy from something that may really need it, like TLS or especially SSH. I've found myself in testing situations where it was faster to regenerate a VM/reflash a Pi microSD than wait for /dev/random to catch up, due to iterating on a writing a script that uses scp or keygen calls. I haven't seen a production issue in a while, and never that severe (eg, HTTPS throttling), but it's happened to somebody I'm sure.
For example, if an adversary with perfect analytical ability learns the outcome of a simulated dice roll you performed using /dev/random, they gain log₂(6) bits of information and you lose the same amount of entropy, irrespective of how many bits you actually read from /dev/random.