Or at least less incorrectly.
These were asserted to be UTF-8 subsets which is totally wrong. Now we decode it as a ISO-8859-1 string. This is also wrong, but it seems the majority of implementations which used TeletexString actually used Latin1 instead of T.61 encoding.
RFC 3280 says that implemenations should try to accept either ISO-8859-1 or T.61 in TeletexString. I'm honestly not sure how or if it is possible to distinguish them reliably.
TeletexString has been "SHOULD NOT" since 2002 so hopefully there are very few such certificates still valid.