Lisa just wants to use it as another way to drag on the attention of having babies, not 1 baby but 2, not twins but premature twins!
She doesn't apply it correctly at all, uses it when suits and luckily for her, her babies are doing very well and look to be meeting their milestones comfortably. For a lot of parents of premature babies the corrected age is so much more relevant as it is more appropriate to where their babies are at developmentally. Lisa is just throwing it out there almost as a brag that her twins are crawling etc even though their only 8 months corrected.
For their 1st birthday we'll get the post of how they are now 1 blah blah blah but we'll get it all again when their due date roles round!
For a normal parent of a premature baby I would take no notice if they did that with the due date post after their birthdays have past, as it is so unbelievable how these babies overcome so much to get to where they are a year later. The pride and relief that their parents must feel must be enormous! But Lisa seems oblivious to a lot of the hardship faced by others