Based upon the 2 photos you published purporting to be of Jack Ruby, it is my humble opinion that the 2 people are most emphatically not the same person. Perhaps additional evidence would dissuade me, but the 2 photos depict 2 different people- assuming that no photographic alterations occurred.
In addition to the very significant difference in scalp coverage, the noses are different, and posture seems different.
On the other hand, the ears look like a good match except at the lobe, and the jowl looks similar.
After looking at numerous pictures of ruby in the getty collection covering at least 10-15 year time span, I would say that the left photo of him at dpd is simply a misidentification. Getty identifies the man as ruby, but it certainly is not. all of the other getty images show a very consistent looking person. This photograph is an outlier.
Having said all that, I suspect that the fake Ruby picture was made to insert into the public record “Ruby” at the DPD to build the case that he was stalking Oswald in premeditation of his murder.