DHL Data Science interview questions

I've applied online for the Data Scientist position at the beginning of February. I was surprised that first person who got back to me was head of business intelligence, who was interested in general stuff like my motivation, background and similar (this was 1st stage - a 30min phone conversation). After that I was approached by head of data analytics to set up an hour phone interview to go over my CV and background (again), and do an analytical case similar to what the team is currently working on. The case considered a market research survey among clients to get knowledge on shipping preferences. I was asked how would I start with data mining in this case - namely data cleaning & cleansing, treatment of null values, treatment of erratic and inconsistent answers. Then I was asked to approach consistency of such 3 questions : 1) 78% respondents said 'yes' to shipping with company A; 2) 71% respondents said 'yes' to shipping with company B; 3) 48% respondents said 'yes' to ship both with company A and B. Task was to identify whether there's something wrong with these percentages. The interviewer was expecting to use Venn diagrams concept, to come up with 23 (i.e.71%-48%) + 30 (i.e.78%-48%) + 48 = 101, which means figures are incorrect somehow. I proposed different method based on playing with data rather than 3 numbers but the interviewer clearly was expecting Venn diagram solution approach, which I was told later on. Last question involved stating a statistical method to see difference between 2 populations (e.g. K-S test or Chi-squared test). The whole interview took more than 1h and concluded with understanding that such business case is difficult to solve over the phone and face-to-face conversation (with pen & paper at hand) would be much better. I was asked about my time availability over the next 3 weeks and assured that the decision on next step (invitation to HQ) will be made within a week. Sadly, within 2 weeks nobody got back to me, and after my second kind request for update (another 2 weeks) I was given the standard "we regret to inform you (...)" phrase from head of business intelligence. Unfortunately, I haven't received any feedback from the business case interview so I don't know why I was rejected. I find such behavior as unprofessional, especially that this is not entry-level position I've applied for.