Ah. This depends whether we are doing drills (not what we call them, but it's what they are) or simulations.
The drills are built around learning a specific movement, technique, or principle, so the attacks there are designed to make those possible. This would be like if I'm training someone to do a high block, I'll have a partner delivering high strikes - low strikes and tackles don't serve any purpose for cleaning up a high block. Likewise, if I want someone to learn to use the principle of aiki, I have to make sure they get an attack at a level that's appropriate for them to find the aiki response. (Quick definition: the difference is mostly whether you disrupt the attack just before it develops power/control or just after, without aiki, it's pure jujitsu - still useful, but requires more muscle.)
For the simulations, we don't have to make those allowances. We train a wide range of responses, some of which are decidedly un-aiki, highly linear, and use force-on-force. This allows even relatively new students to handle attacks (within their personal limits of skill) without having to set up for the specific attack.
So, in parts of training, there's some bias to developing that feel for the moment when aiki is possible (because defense is much easier and more effective if we can access that moment), but our heaviest focus is on realistic self-defense. In fact, part of what I changed in the curriculum was to add two "self-defense sets". During those (the basic set is the first thing any student learns in Shojin-ryu), there is no mention of or practice of aiki principles - just a focus on simple responses to basic, common attacks. During simulations, these are what most newer students will reach for, while more advanced students will be able to access the more "aiki" areas of the art, as well.