Cenaero interview questions

Overall the hiring process was very unprofessional. I applied a researcher position last September, got a first round technical interview in Ocotober and was rejected then. However, this position was posted again in January and I decided to apply again as I was still interested in it. The direct manager replied with interest in my profile and set up a meeting with the team for a in-depth technical interview in March, and followed by an HR interview in early April. All went well and I was informed transparently that I was the only candidate they interviewed and they would like to speed up the hiring process. A non-technical interview was set with the general manager a week later. Three weeks after this, I received a rejection letter stating that they reviewed various candidates they interviewed and decide not to proceed with my application. The reason is that they found me a little weak interms of simulation tools. It is a waste of time and would have better to reject me before the HR and general manager interviews, if the reason was on the technical side. The hiring process lacks of transparency to me, different from what they claimed.