Using the templates found here
Running the commands

job = client.load_table_from_storage(
    'load-from-storage' + datetime.now().strftime('%Y%m%d%H%M'),
    table, gsbucket)
job.skip_leading_rows = 0
job.writeDisposition = 'WRITE_TRUNCATE'
job.field_delimiter = ','
job.begin()

This piece of code appends to my table instead of overwriting it like the docs say.

WRITE_TRUNCATE: If the table already exists, BigQuery overwrites the table data.

I know this because if I use:

table.reload()
print(table.num_rows)

after the job it has increased by 2 million - the size of the table.

I use a workaround as follows:

if disposition == 'WRITE_TRUNCATE':
    schema = table.schema
    while table.exists():
        table.delete()
    table = dataset.table(table_name, schema=schema)
    table.create()

Which seems to work fine, and the while loop is just me making certain that the table is deleted but when I tested it without the while loop it also worked.

Anyway, the issue is WRITE_TRUNCATE isn't doing what it say it does in the docs.