I think if the singularity has occurred, we are also in a period of exponentially accelerating change. As a result of this, the world has been remolded from the earlier strips.
It doesn't really make sense though. The characterizations of AnthroPCs have changed a lot over the course of the comic. I am not sure if this is a result of Jeph having not thought it out fully before or if things are happening the background that we do not see. As much as I like Marten, Faye, Dora, Hanners, etc., none of them are very political or cognizant of the world beyond their own town. The result of this is that while "Big Things" are happening the world, we are not seeing it.
In the era where PintSize was created, it seems that an AnthroPC was seen as more of a commodity to be treated with as the owner pleased. Marten was kind of on the vanguard of well treatment though by holding Pintsize as nearly an equal. He never saw him as just a commodity, so his behavior was not very much shifted by the legislation. This may be part of why we do not see much on the change being made.
Additionally, Pintsize seems to be pleased with their relationship and seems inclined to avoid the responsibility that comes with being considered a full equal. I am guessing that a lot of other AnthroPCs feel that way as well and keep to the "old ways" of interaction in the new world.
Some speculated that Marten was an early adopter of the AnthroPC, possibly given one by his parents.
http://questionablecontent.net/view.php?comic=5 seems to support that notion with Faye not being shocked, but at least mildly surprised by his presence in the way one might have said "Whoa, you got an iPhone?" a few years ago. Also, Pintsize's reaction seems to indicate that he is basic even at that point.
I'm kind of rambling here, but something fundamentally has changed in AnthroPC/human relations in the comic, but it's hard to pin if Jeph had a specific plan for that to occur on the timeline of the comic or if the change is just the result of him fleshing out his world building a bit more than he had in 2003.
As an aside, it seems to me that Momo's personality pretty significantly changed when she got her new chassis. Maybe she thinks of herself as "more human" now that she is in a human-sized body? If I had time, I'd like to archive binge to compare the behaviors.