I think the author knows there are better options for compressing large streams, but still chose to use the situation as a simple benchmark to test the performa

I think the author knows there are better options for compressing large streams, but still chose to use the situation as a simple benchmark to test the performance of his (admittedly trivial) packing and unpacking routines. You're right that the benchmark is biased due to cache effects/etc from processing in a large stream, however. A more honest (and useful) benchmark would be to test the performance of packed and unpacked integers under a random access pattern.