Pluralsight Software Developer interview questions

Fairly standard interview process. Initial HR phone screen. Manager phone screen. Code assessment. A very slow process from start to finish taking about 3 weeks total. Code assessment was average. They claimed it was a new step in the hiring process and asked me to wait for them to generate it. Straight forward assessment building a lightweight package installer (cycle checks, install order, data processing, unit tests). Took a week for them to respond and they did in a rather unprofessional way. What I mean by unprofessional is, very short response saying only that they would not be proceeding with me. No explanation as to why even after I asked the HR representative. At the very least I expect honest and open communication between myself and the HR rep. I felt in the dark durring the entire process. There was a significant time investment by both parties so a 2 sentence rejection email seems a tad rude.