Of course, you must know that I disagree.
All trees change their growth mode(s) shortly after the summer solstice. Prior, there is a brief burst of root growth about the time buds begin to swell, but after that most carbohydrates are consumed making new tissues above ground. Shortly after the passage of the longest daylight day, this slows and more carbohydrate and auxin are available to drive root growth. By this time every species has a canopy of new, highly productive foliage.
One should avoid root work anytime stem extension is occurring as a good supply of water is required (extension occurs by water filling cellular vacuoles, enlarging them before the cell walls are fixed). Some angiosperms, such as maples, and some conifers will produce new stem extensions after the solstice. These times are not conducive to root work, pre/post summer solstice.
No tree grows when temperatures are outside the range of 40F/5C to 95F/35C. The rate of growth increases with temperature above 40F/5C attaining a maximum near, but definitely less than 95F/35C. This is a consequence of the rate of photosynthesis remaining fixed at the same level when it is hotter than 95F/35C, whereas metabolic reactions 'unfixing carbon continue to increase with temperature. Maximum root growth rates peak at much lower temperatures around 70F/25C because they must be covered with a film of water to remain moist (oxygen solubility in water decreases with increasing temperature, whereas the rate at which oxygen molecules move through water increases).
The significance of all this is that trees will, in principle, repair root damage much faster in summer than spring because it is warmer. Of course this isn't the case if daytime temperatures are above 95F/35C for most of those hours, it is not a good time for root work Likewise, it is not a particularly good time for root work if one cannot also keep root zone temperatures in the neighborhood of 70F/25C (get an inexpensive meat thermometer probe and stick it in the pot). In cooler climates where these upper limits are not much of a problem, summer repotting definitely can be better than repotting in spring. The spring repotting window is only a few short weeks long, whereas it is months long after the summer solstice.
In hotter climes, like yours
@Mike Corazzi, it may be nearly impossible to meet these requirements in summer; late-winter/early-spring may well be your only choice. Indeed, you do want to wait until buds begin to swell as this is evidence of root activity. Even in dormancy, trees loose moisture to dry(-ish) air, even if they don't have leaves. The plant must have active root tips to adsorb water. Most water adsorption occurs via extensions of the wall of individual epidermal cells a few millimeters behind the root tip. Lose these in winter and they may not get replaced before the tree desiccates.
It is all very simple.
