It is likely the case that this answer won't be of much use to you as the reasoning in it is mine, somewhat abstruse, and as I do not trust it entirely; so, if it is not perfectly convincing to me there are chances for it to be painful to read in general; it is better however to keep that in mind.
The verb "voir" has been chosen as it seems easier to understand and applies to more familiar contexts.
Comme s'il avait pu voir la mer au loin il pointa du doigt vers l'horizon.
Comme s'il pouvait voir la mer au loin il pointa du doigt vers l'horizon.
Comme s'il pouvait avoir vu la mer au loin il pointa du doigt vers l'horizon.
(pouvoir avoir vu)
In the first the "plus-que-parfait" tells of an action (make out the sea), if it did really take place, that was finished a lapse before the pointing (he stopped looking at it). Here, "pouvoir" has the meaning of "physical possibility".
In the second, the "imparfait" tells of an action that, if it did really take place, was still going on at the time of the pointing. Here, "pouvoir" has still the meaning of "physical possibility".
In the third the verb "pouvoir" does not any more have the meaning of physical possibility, but that of plain possibility.
- J'avais pu avoir vu la mer, mais je ne m'en souvenais pas. (time of reference is the past)
J'ai pu avoir vu la mer mais je ne m'en souviens pas. (time of reference is the present)
The reason the meaning of the verb changes is rather difficult to explain. The "infinitif passé" does not situate an action anywhere as the "infinif" does, an action that the conjugated part, if there is one, will make precise as to which of past, present and future it belongs to, but instead, as the name shows, it represents an action that has been carried out in the past, and as well, an action that has an end in the past. As such it is not subject to physical possibilities since the form implies that it has been realised (characteristic of all tenses which use "être" and "avoir" as auxiliaries).
Après avoir vu le film il lut le livre.
(ref) Comme toutes les formes composées, l’infinitif passé exprime l’aspect accompli et l’antériorité. Il s’utilise dans les mêmes conditions que l’infinitif présent, qu’il remplace lorsqu’on veut ou doit exprimer que l’action est achevée antérieurement au moment de l'énonciation (moment où on parle) ou antérieurement à une autre action.
In conclusion it can be said that "pouvait avoir déferlé" is not proper because the idea of the physical possibility of being washed by a flood without being uprooted is not expressed; instead a different notion is being introduced. What would be said would be much as
- "Comme s'il y avait un probabilité d'avoir vu la mer au loin il pointa du doigt vers l'horizon.",
which is rather meaningless.