BBT chart help

Hannah • 32 yo. 2 MCs. 1 healthy toddler! TTC baby #2

So I did OPKs and felt symptoms of ovulation accurate with the chart below. But my temp rose slowly and then finally spiked today...4 dpo. I confirmed on an ultrasound 2 dpo that I had ovulated. They saw the corpus luteum.

Is it weird that my BBT didn’t spike until now?