calc autofill

Hi
Ive noticed what appears to be an anomaly when using autofill (hope thats the right word) in calc 5.2.2.2 in ubuntu 16.10

To illustrate, open a new spreadsheet and enter 1 in A1 and in C1, and "A1" in D1 and F1.

Select range A1:F1 and fill down to row 2.

Then A2, C2 contain 2 and D2, F2 contain "A2"; note the strings have been "incremented" as well as the numbers.

Undo the fill, hide columns B and E, select range A1:F1 and fill down to row 2.

Now A2, C2 contain 2 as expected but D2, F2 contain "A1"; the strings have not been "incremented.

Does anyone else experience this? It seems véry strange to me but perhaps there is a good reason for it?

(I have often noted inconsistent behaviour when cells contain strings having some digit characters. Personally im not sure that "iincrementing" strings is such a good idea anyway. Sometimes it is a help, often i find it a hindrance. But in any case it would be good to know if precise behaviour is documented somewhere)

Best
Gary