The definition- the only definition- of ES@1 is "everyone starts at 1st level". That's it. He's doing exactly that, and the fact that some of the players made secondary characters is only relevant in that they, too, started at first level.
The definition of ES@1 that typically has contention is when some players are playing high level PCs and new PCs come in at level one. Not when a new PC comes in and the entire table resets to level one. That has nothing to do with the main contention that people have with ES@1.
ES@1 games do work best- as I think I have acknowledged in both this and the original thread on the topic- in troupe-style play with lots of players, many of whom sometimes have multiple pcs in the setting at once. That doesn't mean everyone necessarily switches pcs whenever a new pc comes in, but it means that, eventually, most players have a couple of characters at fairly widely separated levels to choose from for a given adventure. And often, when a new 1st level character comes in, the group will play mostly low-level pcs alongside him or her. That's one way to do ES@1. It's not the only way, but it's probably one of the more common.
But he was not exactly discussing that. He was discussing the table dropping from high level to level one for a new player.
A bit of apples and oranges. You can call that ESQ1 if you'd like, but it's not the same as your troupe-style "everyone is between level one and five and we swap PCs out all of the time" game that you have going on where a ton of players rotate in and out with a variety of different low level PCs.
Some players love switching up PCs and for such a player, switching up a PC when a new guy joins the group or a PC dies might be great.
But many players love the consistency of the current storyline, character interactions, and adventure. Busting that up is just plain annoying and frustrating to many players. They want to continue the adventure and discover what happens next. They don't want to put that on hold and either get back to it months down the road or never.
Getting back to your original post here, you have admitted that you have not tried ES@1 with a large level discrepancy. The people who have concerns with ES@1 often have that as their main concern. So yes, your experience is fine at low levels and probably the same that most other tables would have. But even using his example as ES@1, I do have major concerns with either example of ES@1 here.
1) Having a 1st level PC in a party of 12th level PCs.
2) Having the entire table start over at 1st level because a PC died (or a new player joined).
Both of these seem extremely problematic to me and your experiences at low level seem to be non sequitur to these two problem children here.