It appears that this problem has already been reported on the ESPHome GitHub site:
“Wrong timezone offset when sync time with home assistant”.
There it is explained that the problem is caused by the external newlib library that is used by the ESPHome Time integration, and it is not expected that this issue will get fixed anytime soon.
The solution as given there is to use a timezone format like XXXX-n in the cases that a “<>" format is seen in the TZ data by ESPHome.
Here XXXX is the timezone abbreviation and n is the offset with an inverted sign.
So for instance in Sao Paulo with an offset of -3 to UTC the timezone should be: BRT+3.
However, I think that the disadvantage of this “solution” is that it does not take DST into account, so this has to be set manually when applicable. For instance in Easter Island with an offset of -6 the timezone should probably be: EAST+6 for standard time but EASST+5 for DST.