Question about a solving technique

[SirWoezel]

Hi all,

I am working on a puzzle (sudoku) which ends in a situation where all cells are filled in except these:

 x  x  x  ab x  abc ac  x  x
 x  x  x  x  x  ac  ac  x  x
 x  x  x  x  x  x   x   x  x
 x  x  x  x  x  x   x   x  x
 x  x  x  x  x  x   x   x  x
 x  x  x  x  x  x   x   x  x
 x  x  x  x  x  x   x   x  x
 x  x  x  ab x  ab  x   x  x
 x  x  x  x  x  x   x   x  x

The X's are not important. Only the 7 cells with candidates abc in them are.

As I have blundered with this before, I thought I'd just ask here: is this an ok BUG that allows the solver to deduct that R2C6 cannot be a c (because otherwise you would end up with two solutions)?

Thanks in advance,

SirWoezel