Is windows7's update BOOTMGR designed to waging MBR wars with other os' grub?

The trend observed from windowsxp to windows7 of repeatedly erasing the mbr from the grub of other os and replace with BOOTMGR (after every windows7 reboot) -- then is there such a possibility that in future the hardware products might have some newer features which can impose some terms and conditions for other os from installation unless they fulfill something?
Regarding ntos, If one were to hope for a windowsxp type ntos with more security features but without the MBR-wars unleashed on other os like what the windows7 does, then it implies waiting for years till mingw (gcc+g++) based reactos and its fpos type freepascal-clone-os (with greengnome-shell and freedos-terminal-extension) develop.

yes, what you are saying is true,
to work around this, i think there is a linux boot loader which installs on a USB drive, and thus makes it act as a USB key for loading Linux from your system's Linux partition.

You will just need to google for the name of that Loader, coz i saw it happen at my workplace, and they used a USB key for a particular server in order to boot it into Linux.