Secure boot and JTAG interface

Hi

Based on the secure boot doc SPRUGQ9 in secure enabled OMAP-L138 processors, if the key data contains the JTAGforceOff boolean set the JTAG is permanently off. 

What does that mean exactly? If a JTAG probe is connected before a POR is forced, will the ROM boot loader run?

In other words, if the JTAG is disabled by the ROM boot loader, will it be renabled by forcing a POR?

So assuming someone connects a JTAG probe, power cycle the board, can he then access the flash memory and for example overwrite the key data?

Regards,

Giuseppe