Does buildx build runs steps in a dockerfile parallel

[varunvijayagopal]

I have a docker file like below
FROM %baseImageTag%

ARG LIBREOFFICE_VERSION=7.2.6.1
ARG DOCMOSIS_VERSION=4.7.1

ADD dependencies/repos/ /etc/yum.repos.d/

RUN yum update -y

I need ADD step for yum to find correct reposiotries . But when I execute yum command fails as it fails to find repository where as ADD step says it is completed

#7 [ 2/14] ADD dependencies/repos/ /etc/yum.repos.d/
#7 DONE 2.4s

Is it because copying repo files and RUN step is triggering parallel ? or am I missing something else ?
Is there a way to make it serial if it is parallel ?