What I have heard aikidoists call ki I would define as using visualization to achieve good physics.
Using visualization as a component of training is an excellent way to enhance muscle memory which will help with internalizing the mechanics of technique execution. Ki is something else altogether. Taking the time to visualize a technique before executing it takes one out of the moment, weakening mind/body coordination which will result in one being in less than his/her most dependable and powerful state (no Ki).
The synergy of mind/body coordination (Ki extension) allows the practitioner to perform at higher levels of proficiency than would otherwise be possible in its absence. This is easily demonstrated via Ki testing by having students perform the tests both with and without a high degree of mind/body coordination. Likewise the ability to coordinate mind and body can be strengthened by using the Ki test as an exercise whereby the student is subject to gradually increased loads that require higher degrees of mind/body coordination to successfully deal with.
To answer the question posed in the OP, I'd have to say that no, Ki isn't just good physics (meaning that manifesting Ki is more than correct mechanical execution of technique).