140批准后180天之内跳槽有正式的rule吗

在网上查到的消息是，“180天之内跳槽保留PD，180之后跳槽保留PD并且可以用来续h1b”。但是搜到的都是网友和一些律所的消息，在USCIS的网站并没有找到这个180天的正式规定，请问这个是写在某个rule或者order里面了吗？
USCIS网站我找到的最接近的规定：
https://www.uscis.gov/forms/petition-filing-and-processing-procedures-for-form-i-140-immigrant-petition-for-alien-worker
"The petitioner may request to withdraw a Form I-140 at any time. However, if the petitioner requests to withdraw a Form I-140 that has already been approved for at least 180 days or if an associated Form I-485 has been pending for at least 180 days, we will not revoke the approved Form I-140 and the beneficiary will retain the priority date from the form"

USCIS网站上只有这句话说了180天之后即使雇主withdraw也会保留PD
所以想请问下180天之内跳槽保留PD这个规定有没有在什么正式的地方明确写出呢？或者之前有同学这么操作成功过吗？
不是不相信律所，只是好不容易排到的PD不想冒险，所以想看看正式的法律条文，感谢大家

https://fam.state.gov/FAM/09FAM/09FAM050303.html

9 FAM 503.3-3(C)  Retention of a Priority Date - Employment-Based Preference Petitions

(CT:VISA-300;   03-14-2017

a. Employment Preference Petition Filed by Different Petitioner or According Different Preference:  A petition approved for an alien under INA 203(b)(1), INA 203(b)(2), or INA 203(b)(3) accords the alien the priority date of the approved petition for any subsequently filed petition under INA 203(b)(1), INA 203(b)(2), or INA 203(b)(3).  This priority date is maintained even if the petitioner is different from the original petitioner.  A petition revoked under INA 203(g), INA 204(e), or INA 205 will not confer a priority date.

b. Subsequent Petition in Employment-Based Classifications:

(1)  Unless revoked pursuant to 8 CFR 205.2 for fraud or misrepresentation, a priority date accorded by approval of an employment-based first, second, or third preference petition is retained by the beneficiary for any other first, second, or third preference petition approved subsequently for the same beneficiary.  In all cases, the beneficiary of multiple petitions is entitled to the earliest of the filing dates of the various petitions.

200 发表于 2020-10-28 23:38
https://fam.state.gov/FAM/09FAM/09FAM050303.html

感谢！之前没搜到fam的条例，放心了