I don't know what other's thoughts are on the term show quality, but here are my thoughts on the way I have seen it used over the past decade.
1) Any birds that would be disqualified in a sanctioned APA show is NOT show quality. So any Legbar in a flock that has any physical or general defect including knocked knees, wry tail, squirrel tail, split wing, more than one inch of white on a single feather, feather stubs on the feet or legs, blindness, curled toes, crooked keel bone, wry neck, etc. would not be show quality.
I think many confuse the term "show Quality" because they see advertisements for show quality hatching eggs and thing that means that everything that hatches from those eggs is show quality. The seller can NOT guarantee that everything that hatches will be show quality. The best they can do is a guaranty that the parent stock are show quality, but most so-called "breeders" don't even know enough about the breed they are selling to know if the parent stock are show quality and they are thinking that because they bought eggs from someone that listed them as show quality that their birds are automatically all show quality as are everything they sell to the point that you may get stock going through 2-3 or more people claiming show quality that do no even cull the non-conforming birds from their flock and who have a high percentage of offspring from their flock that would be disqualified if entered in an APA show. If you ever see an advertisement for "show quality" ask the 'breeder" what shows they have taken their birds to and how they did at the show. If they are not showing their birds there is a good chance that they don't know if their birds would be disqualified or not. (Note: I have shown Legbars and some that I thought would get a first place were disqualified for things I hadn't considered).
2) Many birds can make it past the list of general defects and not get disqualified at a show. I got some hatchery Columbian Plymouth Rocks a few years ago. We grew out 15 of them and there were only one pullet and two cockerels in the group that didn't have DQ's (disqualifiers). I took the pullet and one of the cockerels to a small local show (only 31 entries in the open class although over 200 in the youth and 4H classes) and the pullet was reserve champion of the open show. The lesson here is that hatchery birds can be show quality but there are very few that are show quality in a poorly breed line and the measure of the quality of a breeding line is what percentage of the flock conform to the breed standard. Still just passing the DQ doesn't mean that you have a good show bird. If there are 30 birds on exhibit in a category 5 of them will be placed 1-5 and 25 of them will not place. Lines that are bred for show should have a high percentage of show quality birds and be able to produce some winning birds. If it can't produce winning birds then it isn't worth anything to show exhibitors so calling it show quality might be technically true if the birds don't have DQ's but if it can't produce show winners then is it not good enough quality to show and isn't what exhibitors would call show quality.
3) There are very specific requirements in the breed standards. Some are written in a manner that makes it genetically impossible to produce a bird that meets the standard. Some will insist that if the standard is not met 100% it is not correct. My Cream Legbar mentor in the UK that helped me learn the breed when from 2011-2014 had been working with the breed for 6-9 years. She pulled out the standard every year and re-read it with her Legbars right in front of her to compare to the standard. She told me that every year she would learn more and more about the standard and become more and more convinced that she had never seen a Legbar that met the standard and never would. So... there are not perfect birds. None of the Legbars out there meet the breed standard. I just keep the best I have every year based on the rule of tens. That is that I only keep one out of ten that we grow out.
Yours look decent. They crest color is black and should be cream. The tail angle should be 45 degs with the horizon and look to be higher than that, etc. So...there is a lot of room for improvement but since they are only shown against other Legbars at shows and these are likely about the same quality as what everyone else has they are a decent start and can be improved through selective breeding.
Check out the "Cream Legbar Working Group..." thread to see more about the breed standard and how to breed for improvements.