bridge1490, greetings: Regarding the link you posted, there are times when one falls into the trap that if it is on the Internet, it must be true. The directions for erasing free space are correct, the allegation that by doing so will have a positive impact on performance increase is NOT correct.
Note that there is absolutely no mention of any degree of performance increase that one might expect from erasing free space. The only way to determine the veracity of such an allegation is to test in a controlled environment with two identical MBPs with identical data and then perform accurate measurements. Unless one has such a point of reference, any perceived performance increases are illusory.
My comment is simply to make the relevant facts to be correctly understood by others who may read this discussion.
Ciao.