is this a bug or intentional

[roadrunner]

I did the following in the spreadsheet app:

1. Named column A1 “DATE”; *edited* named column A, not column A1
2. Selected cell A1 and typed in 2015.1015;
3. Selected cell B1 and typed in =DATEADD(A1,5);
4. Tapped CAS and OK (I got the expected 2015.1020);
5. With cell B1 selected I pressed shift-copy;
6. With cell C1 selected I pressed shift-paste, then selected 1 from the list and then formula.

Instead of the expected 2015.1025 I got =B1ADD(B1,5)

FYI: software version 8151, hardware version C

-Road