Mendix Senior Frontend Developer interview questions

The interview process until the last part was nice but the way they evaluated the technical challenge was weird and imho not just. They asked me to recreate a part of their website which was made using jQuery, which I rewrote using pure JS, shortening it to ~400 lines of code from the original ~1600 and it worked faster than the original solution. They then said I "copied a lot of code from the original" by which they meant the ~10 lines of code which simply sorted an array. I wrote them back explaining why I thought their evaluation was unfair and that I thought it was weird that they thought someone interviewing for a senior position wouldn't know how to sort an array and asked them whether they would reconsider, or in either case give me pointers on what I could do better. I got completely ghosted thereafter. They could've just said no and I would understand.