I did a quick performance test using Symfony and got the following results:

Before PR:

Building...

real    15m51.610s
user    6m55.666s
sys     7m22.764s

After PR:

Building...

real    16m40.861s
user    7m12.818s
sys     7m40.737s

Could you provide me with your own benchmarks with details on what you built to perform the test?

I was finally able to test this. The PR improves performance on HDD but you are right, it really does decrease perf. on SSD (or any other fast IO drive, e. g. /tmp mounted in RAM).
As such, I leave the decision whether to pull this up to you.
Moreover, It may be useful to update the documentation and add some recommendation about creating and building a phar on fast drive/storage and than moving it to the target location.