I have a simpler explanation. 300 Million years ago the seeds did not have a hard outer shell and there were few animals to eat their seeds so the tree needed no defense mechanism. As animals evolved, more began eating the seeds so the tree evolved a defense mechanism and through natural selection evolved a relationship with the Dodo to propagate.
Occams razor.....
Maybe...but how do the tree know its seeds aren’t germinating? Takes inventory and sez, hmmm I had all these seeds but I ain’t seeing any saplings? Wonder what happened.
Never mind even being aware of second party seed dispersion some distance away.
Then there is that trivial thing of identifying the cause of failure as being covering material strength failure and calculating the appropriate increase in thickness sufficient for needs of seeds.
What’s the mechanism that determines the amount and type of material needed. Long way between a very modest thin and soft seed covering and the shell of a walnut or Brazil nut.
You see where this is heading?
;>)
Most likely.