I will write by a nexample on Xiaomi Mi 10 Pro 5G China variant, rooted, with enabled QXDM diag port.
In EFS there is a file china_msim_restrictions.xml which contains the following section:
<rf_band_list ns="global" name="post:disable_NR_bands">
<gw_bands base="current" />
<lte_bands base="current" />
<tds_bands base="current" />
<nr5g_sa_bands base="none" />
<nr5g_nsa_bands base="none" />
</rf_band_list>
<if>
<all_of>
<subs_is_active subs="this" />
<subs_is_active subs="other" />
<not> <location_mcc_in list="post:china_mccs" /> </not>
</all_of>
<then>
<rf_bands list="post:disable_NR_bands" />
</then>
<else>
<rf_bands list="post:default_bands" />
</else>
</if>
which basically means, if you do not have China's SIM you will have 5GNR bands disabled