There were not any additional locks. The only difference is that OSG tried to assign threads to cores manually instead of allow OS to do this job, and did not manage to do it well on some Linux setups when using stock OSG instead of scrawl's fork, what could lead to large performace drops.
There should not be any difference in other cases.
Again, if you encounter any issues which are not present in the 0.45 release, use a bisect (either git bisect or just try to install different nightlies) to determine when this issue appeared.