KL17 reference manual V4.1 and V5.1 with updated Figure 13-2. Kinetis Bootloader Start-up Flowchart at page 179
There with modification to add "is direct boot valid" check.
Please check below picture for the detailed info:
The "is direct boot valid" check function is not supported for KL17 product, the correct flow chart should be below:
The "is direct boot valid" check function is reserved for further parts(such as KL82), which has one bit in BCA filed to control running code in QSPI Flash or internal Flash:
Thank you for the attention.