We use hidden field to indicate that the option checkbox was rendered.
The support for the hidden field was added in Woo 4.6.0 (51afe3207a (diff-019fb1a3da8e1f8d9f148c7407195e640587dfeb3e7830ef8e8fa6f29aa0a6ed)
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This commit adds a workaround that can be removed we drop support of older WooCommerce versions.
[MAILPOET-3772]