Why the change in the Isshinryu drop to the floor in Kusanku kata?

 I wonder often what went through the mind of Shimabuku Tatsuo when he made changes to the kata as he was taught by Kyan Sensei.

 In particular the drop to the floor done twice in the Shorin Kusanku Kata. From the first time I saw it I never could really work out why it was done that way.

 

 

I used this video as the source for the movement analysis. 

 

 

 

 

 

Perhaps it was used this way from another Bing photo I found. Just an assumption on my part.

While I was shown this movement by Carl Long from his Shimabuku Ezio derived Shorin Ryu, it never made sense to me.

 

Where the Isshinryu version I was taught by Charles Murray was done like this.

 I used this video of Young Lee as source  https://www.youtube.com/watch?v=1BzGK-wRtr8

 

 

 

Which is an entirely different movement when the drop to the floor takes place. The Isshinryu version drops to block/strike into a kicking leg and then rises to strike that opponent.

Of course as an Isshinryu stylist that makes more sense to me. But I do wonder what was going through Tatsuo’s mind when he originally learned this, that led to his change?