As Martin said, a player can quickly raise their rating if in fact they be stronger. It is only natural for all new players to want the highest rating (1800) when signing up. I agree, this needs to be changed as most are well below this in reality. 1800 is in the top 3 to 4 % for online anyway.
1 side affect is detrimental imo. I'm around 1900 and my seeks often include 1800 (online). I constantly am aborting challanges by new 1800 players. I will not play a provisional rating that is most likely in error. Everything to lose and nothing to gain. There are other reasons of course which are understood. A 1200 can reach 1800 and establish a profile and history of fair play in a short time.
Where whould I suggest chess.com should return to 1200 for all new players (unless titled)?
It's not just the phone app but v3 as well. However, since their RD will be high, it shouldn't really have much if an impact as they will quickly drop to where they should be or rise up as the case may be.
Based on the help article, I guess you are right. I was remembering incorrectly. However, based on those game results, the site may have implemented someting similar to combat rating manipulation.