@Yuuki Kirie and Keiko are from a period where Mecha weren't prioritized by the Army, and were 'as close to a Power Armor as a Mecha could become'. That being said, there are differences in use and training. Though a pilot that has been trained in a Mindy can make a Kirie/Keiko move to a sufficient degree to fight, the Kirie/Keiko isn't as constrained to humanoid form and range of motion as PA due to the joint systems. Though the relative range of motion between the Kirie/Keiko and the Ryoko isn't known, it is still the case that the sensory, electronic, and control systems are largely common between them. As such, it is best to group the Kirie/Keiko with Mecha from a training perspective while noting that they overlap with Power Armor from a deployment perspective. Added training for building infiltration is also required because their larger size but ability to depart humanoid form to perform improved navigation maneuvers results in a rather different set of skills from Mindies and a completely missing set from the Ryokos.
It should also be noted that a Mindy-scale Mini-Neko THOUGHT Armor is also something I have wanted to see for a long time, something that carries all the properties of a Mecha in terms of operation and training. There are a number of benefits to such a system that are not immediately obvious but allow for a niche to form when combined. I suspect that such a unit would join the Kirie/Keiko in an 'intermediate' niche of Mecha that, while sometimes fielded like Power Armor, would borrow heavily from Mecha training doctrine. As such, this future possibility should also be considered when structuring this program.
My opinion is that Kirie and Keiko should be considered mecha, more for their training requirements than size, but that their deployment will almost surely overlap with Power Armor doctrine...and a Mini-Neko mecha would be even more so. As such, some interaction between the groups should be expected and accounted for.