Concatenation of adata and losing .var

Question

[bioinfo]

Hello,

I am trying to use ad.concat (adata = ad.concat(adatas, label="sample"")) to merge 2 adata objects but I lost the .var layer.

I found this link https://discourse.scverse.org/t/loosing-anndata-var-layer-when-using-sc-concat/1605/2 that discussed the issue.

However, I also noticed that if I do adata = ad.concat(adatas, label="sample", join="outer", merge="same") the .var layer was preserved. Is there a reason why I should do the concatenation using the information from the link and concatenating the .obs and .var separately instead of using the below?

 adata = ad.concat(adatas, label="sample", join="outer", merge="same")

Thank you