Sorry if this is the wrong tracker.
A user pointed out that GOIDs are listed in the "External references" section on the gene pages for AmiGO:
http://amigo.geneontology.org/cgi-bin/amigo/gp-details.cgi?gp=UniProtKB:P01375
The sequence loader reads the uniprot_sprot.dat.gz
uniprot_trembl.dat.gz files.
DBXREFs are extracted from this file: http://www.genome.jp/dbget-bin/www_bget?uniprot+P01375
Everything, including GO terms with a DR flag (1st column) are imported (from what I can tell... this is mystery Chris code in GO::Model::Xref).
Yes, we attach all sequence dbxrefs to the sequence when loading.
Perhaps the most sensible behavior is to filter out dbxrefs from the sequence to GO
DR GO; GO:0006927; P:transformed cell apoptosis; IDA:UniProtKB.
It has the evidence codes listed so looks like a duplication of the annotation.