I wonder if this may be deliberate - phoneposting is commonly seen to be detrimental to the quality of discourse (for various reasons e.g. it is trivial to evade bans, phone users tend to join and leave threads randomly due to IRL concerns, phones do not tend to have good image organisation so phoneposters do not contribute topic-appropriate memes, and so on). I will be interested to see if raising the barrier to entry for phoneposters improves the overall quality of the imageboard.