No one is arguing, 'cellphone, hence no poverty'. People are merely arguing that the lowest 10% are no longer destitute.
Historically, "Bread and circuses" is sufficient to keep disgruntled poor masses just disgruntled but not revolting; regimes get overthrown either when the rulers can't provide bread anymore, when they do unbearable physical harm (e.g. disappearances, torture, etc), or when an external force comes in. And currently it's not a big burden on the economy to just provide lots of cheap food and entertainment for everyone to pacify them, that can be done with just a few percent of GDP.
The parent comment certainly does. Specifically mentions "things that used to be luxuries" being available to the poor as a reason.
Homelessness means no shelter from the elements or people that want to hurt you, possessions beyond what you can carry and defend, no health care, and being treated like a second class citizen.
Also, having seen the situation in third world countries, I have a real issue calling American homelessness destitution, but I understand the arguments from social cohesion.
[1] https://www.nlchp.org/documents/Homeless_Stats_Fact_Sheet [2] http://homelessresourcenetwork.org/wp-content/uploads/2011/0... [3] https://www.spur.org/publications/urbanist-article/2017-10-2...
Homelessness, in general and in SF, is overwhelming caused by economic issues.