As you can see here, here, and here, chrono doesn't pass options.timezones onto toTimezoneOffset as would be expected. This means that anything passed via ParsingOptions#timezones has no effect whatsoever. I'd appreciate a release fixing this ASAP, for now I'm using a locally patched version with these changes:

// chrono.ts#L156
this.reference = new ReferenceWithTimezone(refDate, option?.timezones);
// results.ts#L14
constructor(input?: ParsingReference | Date, timezoneOverrides?: TimezoneAbbrMap) {
// results.ts#L21
this.timezoneOffset = toTimezoneOffset(input.timezone, this.instant, timezoneOverrides);