This reads like an incredibly poorly researched article. As in, it sounds like it was written after an hour of googleing and skimming a few of these guides.
It might be interesting to get the opinion of somebody who tried this, mostly out of curiosity.
1. One of the core guidelines is "Don't question it. If you think you may have heard a voice, it was your tulpa." - This becomes important later on
2. True 'sentience', in the meaning that there's a different entity that thinks in parallel to you, is something that seems impossible to achieve. There are a few people who claim that they can do that, but nobody seems to be able to replicate that and at this point I believe that some of the people who think they have a very well manifested tulpa actually suffer from real mental issues that get misinterpreted as tulpa.
After some (a lot) of time spent on creating the Tulpa, I did actually hear a voice that at first surprised me. It genuinely felt like I might be talking to a different person. A huge success, surely, how is it possible that nobody talks about this. However instead of not questioning it, my inquisitive and critical side took over to figure out how it works.
These are my personal findings:
The process of "forcing" a tulpa, not dissimilar to meditation, conditions yourself to:
a) Build a well thought out alternate personality
b) Disassociate certain thoughts from yourself and attribute them to the tulpa
c) Rapidly context switch between two personalities while maintaining the illusion that you are not in fact talking to yourself
In summary, you're training yourself to context-switch and impersonate an alter ego, while also crafting a strong conditioning to ignore that process and instead attribute it to a sentient thought-form