Hi Kthomp19 -
I've done some searching for Growth Fund holdings of Fannie Mae preferred, and as you have said, there does not appear to be any way to access the holdings history from the American Funds website.
I did manage to get a few tidbits from the Yahoo Finance website. Under their "holdings" catagory for FNMAS and FNMAT, their published numbers lag the numbers shown on the Growth Fund of America site. I've cross-referenced these numbers from Yahoo before, for FNMA and FMCC, and they have been accurate for the common shares. The numbers only go back one quarter, though. Here they are:
FNMAS
12/30/18 (Yahoo site) - 30,932,995
3/31/19 (Growth Fund site) - 33,403,557
+ 8%
FNMAT
12/30/18 (Yahoo site) - 16,806,326
3/31/19 (Growth Fund site) - 16,806,306
no change
The Growth Fund site also is showing some Fannie Mae series' "O", "P" and "R". I was unable to get any numbers for these issues off of Yahoo Finance.
One thing for is for certain: many more funds are indicated as holding significant amounts of Fannie preferred shares than Fannie commons.