Why do people say that Yasuo has a weak lane phase?

PS: This is not a thread asking to nerf Yasuo or to say that he is OP.

I just want to know why people believe that Yasuo has a weak lane phase. In fact, from my experience it is the complete opposite: Yasuo's lane phase is either oppressive against certain matchups, or even against others. There are very few matchups where he is actually weak against.

With Yasuo's shield, low cooldown Q, and constant mobility with E, it is very hard to actually be able to trade with him. It is also difficult to poke him because you have to bypass his shield and even then, many pokes are skillshots, and it is difficult to land a skillshot with Yasuo's ability to move between minions; which is especially strong during the lane phase. For example, with Cho'Gath (which is one of Yasuo's hardest counters) I actually have to play safe until level 3 which is when Cho is actually going to start countering Yasuo. He needs all his abilities to be able to reliably counter Yasuo and during the first 2 levels he is vulnerable to all ins.

To be honest I actually find Yasuo to be easy to deal with AFTER the lane phase, even with the fact that he scale well with items. Unless Yasuo is very fed or if his team has lots of knockups, Yasuo is not going to be a threat after the lane phase. Also, during the mid/late game it is actually easy to burst Yasuo down through his shield, whereas during the early game many champions don't do enough damage to be capable of that.

Where did this myth that Yasuo has a weak lane phase came from? Is this due to Yasuo's latest nerfs to his shield and base HP?