Was never my intent to make seem like player data is your only more so that data uploaded does record everyone in said group, which for some could been seen as problem, not the fact that a player uploaded their own log which happened to contain data surrounding players as the problem. Was not sure how to word, as I have English is not my strong suit, so at times my word choice leaves much to be desired. My stance is that if it was opt-in people can still upload data just the data uploaded would simply blur or remove data of an unclaimed character. Not that people should not upload logs or try to prevent others form uploading as a means of protecting their parse.
I also would not say it is paranoia, use to help with an anime streaming site (use to upload, and help encode ) and one of the reasons I stopped helping though time being the major one, said site would change their polices as the seasons changed especially around data. Also they changed how you earn points, which could be used to bypass ads and took them away from people due to policy changes. Not going to pretend I understand the legal aspect of said actions, but I personally take polices of any site with a grain of salt.
I get their will always be a bottom, but should that bottom be comprised of players that have no desire ( yet do not know you an hide logs ) or even know about FFLogs? Also regarding your example wouldn't you still be able to come to said conclusion, while it would be a smaller sample size unless many people remove their logs from the site there should still be a wide array of logs of varying skill levels to show that BLM is lagging behind across the board. As I said only way I could see balance scanning not being possible is if not enough people upload logs that contain BLM data. Though in the end I am sure SE also has their own logs that they use to make balance changes.
I take all polices from all sources with a grain of salt, and while I do not trust SE, I value them more in the sense that they stand to lose more from shady policy changes. That is why I would be more inclined to fully endorse an officially supported parse instead of FFLogs, and say if the SE logs functioned just as FFLogs did now, at the very least people would be informed about them from the start and if they wanted to take part they could and if not they could opt-out as they are creating their account. If people were more aware of what FFLogs were about how you could go about making data hidden I really would not have much issue with it. As it stands only way for a person to know about FFLogs is either to be told either in a positive or negative way, have past experience with a parser, and or hear about through the grape vine youtube, reddit, forums etc. . . so while I do not trust SE per se, I do think that if the had their own logs the info as to what they are and how to not be part of it would be more transparent and no matter how trivial of an effect it would have at the very least the player would have control if the data is shown or not.
Though I do understand that all data is important, I just simply cannot wrap my head around why the player base needs to see names tied to said data. One of the main reasons why I do not upload data from when I pug, since while I may have had a good run, I have no clue how to just upload my numbers and not the rest of the group. So I refrain from doing. While I would have loved to do this with our own group, just was not possible since I can tell you without FFLogs no way in hell would we have figured out how to make better use of our time and play during an encounter. I know it is a weird point. I refrain from upload data from pugs since I am not sure how to go about just uploading my personal numbers, and not sure if I can blur out the names if I upload, and I am also not going to ask everyone in the group if they are cool if I upload the data, just I simply upload data from my groups runs.
I guess I sort of see it as how people blur out names in screen shots regarding chat logs on the forums, I am not sure if they have to do because of the forum policy or out common courtesy. I would say let the same practice be adopted by FFLogs, but that would be unreasonable to expect players to run by everyone in the group they would be okay if they did not blur out their name on the logs. I do not know making it so it is anonymous I think would go a long way. Lol but have no way to prove that.