Description for large_blocks feature states the following at the end (verified manpages for 11.4-R, 12.1-R, and HEAD): "Please note that booting from datasets that have recordsize greater than 128KB is NOT supported by the FreeBSD boot loader." However, this has been fixed in r328866 more than 2 years ago.
A commit references this bug: Author: allanjude Date: Wed Jul 15 14:38:16 UTC 2020 New revision: 363224 URL: https://svnweb.freebsd.org/changeset/base/363224 Log: zpool-features(7): Note that the boot loader has support for large_blocks Since r304321 (-current: Aug 18, 2016) and r328866 (stable/11: Feb 5, 2018) the FreeBSD loader has supported reading from datasets with the large_blocks feature active. PR: 247992 Reported by: Anton Saietskii <vsasjason@gmail.com> MFC after: 2 weeks Sponsored by: Klara Inc. Changes: head/cddl/contrib/opensolaris/cmd/zpool/zpool-features.7