Question about trusted_validator_set in detect_misbehavior

[beer-1]

In detect_misbehavior, hermes is fetching trusted_validator_set at trusted_height not trusted_height+1 and check this result with trusted_validator_set in update_client ibc events.

hermes/crates/relayer/src/light_client/tendermint.rs

Lines 176 to 185 in 9e1b91b

	let trusted_block = self.fetch(update_header.trusted_height)?;
	if trusted_block.validators.hash() != update_header.trusted_validator_set.hash() {
	return Err(Error::misbehaviour(format!(
	"mismatch between the trusted validator set of the update \
	header ({}) and that of the trusted block that was fetched ({}), \
	aborting misbehaviour detection.",
	trusted_block.validators.hash(),
	update_header.trusted_validator_set.hash()
	)));
	}

But when hermes makes MsgUpdateClient, it is always fetching trusted_validator_set at trusted_height+1 like following. (see line 369, 388 and 401)

hermes/crates/relayer/src/light_client/tendermint.rs

Lines 369 to 414 in 9e1b91b

	let trusted_validator_set = self.fetch(trusted_height.increment())?.validators;
	let mut supporting_headers = Vec::with_capacity(supporting.len());
	let mut current_trusted_height = trusted_height;
	let mut current_trusted_validators = trusted_validator_set.clone();
	for support in supporting {
	let header = TmHeader {
	signed_header: support.signed_header.clone(),
	validator_set: support.validators,
	trusted_height: current_trusted_height,
	trusted_validator_set: current_trusted_validators,
	};
	// This header is now considered to be the currently trusted header
	current_trusted_height = header.height();
	// Therefore we can now trust the next validator set, see NOTE above.
	current_trusted_validators = self.fetch(header.height().increment())?.validators;
	supporting_headers.push(header);
	}
	// a) Set the trusted height of the target header to the height of the previous
	// supporting header if any, or to the initial trusting height otherwise.
	//
	// b) Set the trusted validators of the target header to the validators of the successor to
	// the last supporting header if any, or to the initial trusted validators otherwise.
	let (latest_trusted_height, latest_trusted_validator_set) = match supporting_headers.last()
	{
	Some(prev_header) => {
	let prev_succ = self.fetch(prev_header.height().increment())?;
	(prev_header.height(), prev_succ.validators)
	}
	None => (trusted_height, trusted_validator_set),
	};
	let target_header = TmHeader {
	signed_header: target.signed_header,
	validator_set: target.validators,
	trusted_height: latest_trusted_height,
	trusted_validator_set: latest_trusted_validator_set,
	};
	Ok((target_header, supporting_headers))

Is it intended or bug?