V4 vs v4-nonUKB CFTR F508del

Hello - Regarding the F508del variant, the European (non-Finnish) population in v4 has 49 homozygotes, while v4-nonUKB, which has a much smaller sample size, has 47 homozygotes. I’m unsure why the UKB samples had fewer homozygotes. Is this expected? Thanks!

Genetic Ancestry Group Allele Count Allele Number Number of Homozygotes Allele Frequency
European (non-Finnish) 17610 1178514 49 0.01494

|Genetic Ancestry Group|Allele Count|Allele Number|Number of Homozygotes|Allele Frequency|
|European (non-Finnish)|5465|417886|47|0.01308|

We have investigated this and discovered that a high number of these homozygous cases originated from a pulmonary clinic recruitment effort within a large healthcare biobank dataset included in gnomAD v4.