The diagonal of the 70D 22.5x15mm sensor is 27.04mm.
The diagonal of the 700D 22.3x14.9mm sensor is 26.82mm.
That's a difference of less than 1%.

The smallest APS-C sensor Canon has released is 22.2x14.7mm (EOS 1100D/Rebel T3).
The largest is 22.7x15.1mm.
This sensor first appeared in the 10D which was introduced before the EF-S lens system. EF-S lenses will not mount on the 10D, only EF lenses will. The EOS 300D/Digital Rebel, which is EF-S compatible, later had the same sensor.

The difference between the diagonal of the smallest and largest APS-C sensors Canon has released to date is only 2.3% (26.63mm vs. 27.26mm).

The diagonal of a 24x16mm sensor that yields a 1.5X crop factor is 28.85mm That's 5.6% wider than the largest APS-C sensor Canon has ever released.

I would be very surprised if Canon's current EF-S lenses would cover such a diagonal without significant light drop off in the corners.

Beyond that, though, your question may be making more of a 5% difference in the linear sizes of sensor than what is actually there. The differences in image quality between sensors has a lot more to do with other factors than a 5% difference in linear size. Just look at the improved performance at low ISO of the newly released 80D, with a 22.5x15.0mm sensor, compared to its predecessors.

Further, the perceived difference in the marketplace between sensors measured by testers such as DxO Mark and compared at ISO 100 but often used at ISO 1600 or 3200 is often more than the actual difference in real life situations. Especially when some cameras are tested using their manufacturer's own demosaicing algorithms and others are not tested using the manufacturer's own algorithms, but rather algorithms developed by the testing organization.