say command says wrong text (for some voices)
These voices come from Nuance. If you try their Vocalizer Demo you can hear that "seq" is replaced by "the following" there as well.

This appears to be similar to Nuance's recognition of "homographic abbreviations", where Nuance will attempt to convert an abbreviation into the full word.

I have noticed that there are other words that are interpreted


e.g. "for example"
sat. "Saturday"
mar. "March"