For reference, here is the
current Canadian citizenship act and here is the
easier-to-read version from the Canadian government website.
Based on what little information Bob2 provided, his grandmother was probably born in Canada, but moved to the US, married, then had Bob2's mother before the commencement of Canadian citizenship in 1947. However even though it seems that his grandmother got citizenship in 1947, his mother was never eligible for Canadian citizenship because the 1947 Act did not allow married women to pass on citizenship to their children.
Bob2's mother became a citizen under paragragh 3(1)(q), which is if the person was born outside Canada before 1947 and did not become a citizen to a parent who did became a citizen in 1947.
Bob2 would be described under paragraph 3(1)(g), which is the first generation born outside of Canada but was never eligible for citizenship, because his mother was still not eligible for citizenship when he was born in 1962.
If you look at the first generation limit under section 3(3) and 3(3)(a), it says:
3(3) "Paragraphs (1)(b), (f) to (j), (q) and (r) do not apply to a person born outside Canada [a] if, at the time of his or her birth, only one of the person’s parents was a citizen and that parent was a citizen under paragraph (1)(b), (c.1), (e), (g), (h), (o), (p), (q) or (r) or both of the person’s parents were citizens under any of those paragraphs"
Now, if you were to interpret that section to work with Bob2's situation, it would read like this:
'Paragraphs (1)(b), (f) to (j) [f,g,h,i,j], (q) and (r) [does] not apply to a person born outside Canada if, at the time of his or her birth, only one of the person’s parents was a citizen and that parent was a citizen under paragraph (1)(b), (c.1), (e), (g), (h), (o), (p), (q) or (r) or both of the person’s parents were citizens under any of those paragraphs'
which I interpret as 'because Bob2 is described under 3(1)(g), he is not a citizen because his mother is a citizen under 3(1)(q).
So to me, as I interpret the law, the generation limit supersedes retroactivity. If it was not meant to be interpreted this way, then it would not have been explicitly stated in the Citizenship act.
I did not find any mention of retroactivity in conjunction with second and subsequent generations in that analysis; even in section B that explains the need for retroactivity, the connection is not made between the two. So I believe it was understood that retroactivity was not meant to a pathway for second and subsequent generations to acquire citizenship by descent.