UPDATE and Answer:
I modified my approach and went back to the original source data which was not part of a pivot table and was able to use a simple match formula between the 2 data sources. So, my original data looked like this:
+----------------+---------+--------+--------------+
| Gtin | Brand | Name | TaxonomyText |
+----------------+---------+--------+--------------+
| 00030085075605 | brand 1 | name 1 | cat1 |
| 00041100015112 | brand 2 | name 2 | cat2 |
| 00041100015099 | brand 3 | name 3 | cat3 |
| 00030085075608 | brand 4 | name 4 | cat4 |
+----------------+---------+--------+--------------+
I had another sheet containing the data I needed to match to in this format:
+----------------+---------+
| Gtin | Brand |
+----------------+---------+
| 00030085075605 | brand 1 |
| 00041100015112 | brand 2 |
| 00041100015098 | brand 3 |
| 00030085075608 | brand 4 |
+----------------+---------+
I created a new column in my source sheet and used a if error match formula:
=IFERROR(IF(MATCH(A14,data_to_match!$A:$A,0),"yes",),"no")
Then copied this formula down for every row, about 75K rows which very quickly added a yes or a no.
+----------------+---------+---------+--------+--------------+
| Gtin | matched | Brand | Name | TaxonomyText |
+----------------+---------+---------+--------+--------------+
| 00030085075605 | yes | brand 1 | name 1 | cat1 |
| 00041100015112 | yes | brand 2 | name 2 | cat2 |
| 00041100015098 | no | brand 3 | name 3 | cat3 |
| 00030085075608 | yes | brand 4 | name 4 | cat4 |
+----------------+---------+---------+--------+--------------+
The final step was to just filter for Yes values and I had all the data that I needed.
My mistake was going to a pivot table first which put the data in a very funky format causing me to have to do a transpose, which wasn't really necessary. Hopefully this can help others....