^That is my understanding of it as well.
Pseudo Elemental is something that is able to benefit from converting, but is not able to hit something that has 0% to neutral.
Forced Neutral is something like Guillotine Fist and Acid Bomb, which will not even benefit from converters.
Another thing to remember is that Status Atk is always neutral (unless someone is using Mild Wind), therefore the portion of damage from ANY skill which has Atk in it, will be reduced by GR Card according to the attacker's Stat atk.
GR does not, however, help with the Equip and Weapon Atk portion of a converted pseudo-elemental skill (like Tiger Cannon).
Gates of Hell is something of a special case. It has two parts in its formula. First is the standard atk part. This is pseudo elemental, and if used with converts, it will ignore GR card and neutral element reductions. The second part, which is the Missing HP portion, is forced neutral, and is also completely unreducable by all means, except for GR Card, Energy Coat, and WoE reduction (50%). The second part is functionally similar to Rapid Throw.