Is it normal to get a dye stealer the day of your missed period?

I’ve always tested 9-10 dpo so I’m used to slowly seeing the line come in. Even so, my dye stealers were closer to 18 DPO. This is the day that I was expected to get my period (tested bc I had no PMS symptoms) and took 4 tests because I couldn’t believe how dark the line was. happily surprised but shocked!