As I understand it from electronics school many years ago, (44 years ago), plus a recent review: An aluminized crt does not have a gun with an ion trap and does not require an ion trap magnet. The electron beam has ions mixed in with it that will damage the screen phosphors causing a dark spot in the center of the screen. The very thin aluminum coating has many tiny openings in it which will pass the electrons but will not pass the ions which are of a much greater mass. On a non-aluminized crt, an ion trap, (bent gun, tilted gun, or tilted electrostatic field) aims the electron-ion beam towards the side of the crt neck, or in some, the side of the second anode. The ion trap magnet is used to deflect the electron beam back to center but will have little effect on the ion stream which hits the inner side of the anode, or the side of the neck. If you have a spot of light or a raster on the screen without an ion trap magnet, then obviously you don't need a magnet to straighten the beam. You don't need an ion trap with an electrostatically deflected crt, because the electrostatic field will deflect the ions as well as the electrons, and the ions won't be concentrated in the center of the screen and damage it.
Donald