publishers being on facebook doesnt mean there are demand, they can be scams. I remember one scam publisher called blackshellmedia who only posted twitter post or facebook post then do nothing but take a percentage each time. https://www.reddit.com/r/KotakuInAction/comments/43bo19/a_company_called_black_s...
Actually since i think about it, when facebook remove the targeted ads, there has not been any legit reason to use facebook. Anyone can make groups on other sites, reddit has automod so it makes things easier to mod while facebook lacks mods and paying people isnt the best thing for a company. Many gamedev groups are mislead people who still believe steam and unity are good starting line for gamedev.
Many professionals wouldn't even go to facebook first, they would go to twitter because they can embed tweets while facebook lacks such features as well as blocking people from seeing post, making facebook a guarded community. Actually since the goal of marking is to get everyone in the whole world to see your product, using facebook will only give you facebook users not new customers. This also goes into how your post is seen, facebook will not promote your post it doesnt have such thing nor can people searching on google find it. That just means twitter has better SEO with tags, retweet and easy ad placement on people who follow them.
back on the topic, wishlist is not accurate 400 =/= 400. As stated on steamwork: https://partner.steamgames.com/doc/marketing/wishlist
unless all 400 did not opt-out of emails (which is very unlikely) you may get people buying but since no one likes having ads pop-up on email that 400 becomes somewhere to 100 or less. Even then with legit players, you have to see things from their view, your game is next to many other wishlist. If you have 400 wishlist, you have to assume each player has more choices or better, thus making wishlist a double edge sword where you have people but dont have them.
When i hear people say "oh steam sells are higher than itch or gamejolt", i know why such statements are said. You never promoted any other platform. If you only promote steam store for your game, people are going to steam, it's basic marketing 101. I seen so many people promoting only steam and then soon after a few days the game launches on itch.io/gamejolt. If you were to do the same thing with Steam then the same result is going to happen. There is also many people in GOG who hate gamedev who lie to them about their release for GOG store but never got approved or tried. The next time they see the game it's on Steam and only on steam with steam API related services needed to work. Making that game unable to go to GOG or itch.io because the gamedev doesnt know how things work without steam.