Odd interaction between tab and backspace

[Mark Yagnatinsky]

I'm new to this list, this is my first message; I subscribed less than
an hour ago.  Please be gentle if I break etiquette.

I've tried the following in mintty and in putty, and it happens in both:

First, launch cat or grep or similar.
Type a line with some tabs in it.
Try to backspace them away.

The tabs are erased one space at time, leading to ... You know what,
why don't I just show you:

$ cat
0       1       2       3       4       5       6     eh?
eh?

The above was produced by typing 0 through 9 separated by tabs, then
backspacing as much as possible, then typing 'eh?'  The screen still
shows 0 through 6 followed by eh?, but all cat got was the eh?!

Is it a bug, a feature, or something else?

Thanks so much!

P.S. This is my third attempt to send this message.  First I sent an
html email, then I forgot a subject.  Third time's a charm?

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