Freckles not any darker after BBL on face. Is this normal?

Usually brown spots and freckles start darkening after several minutes but are at their darkest over the next few days before the pigmentation sheds off.  I would be patient and see what happens.  It's possible you may need additional treatment(s).

Excellent question. I would suggest waiting a few days to see the effect on the areas you are concerned about. If they do not get darker, I recommend seeing the practitioner who performed the BBL because you may need further treatments. Sometime the settings may need to be modified to achieve a better effect. Hope this helps. 

If this is your first treatment, the practitioner properly chose to start less aggressively to check for your skin's reaction in the coming weeks.  Not all freckles get darker immediately, although most do, but they may improve without any darkening .  The more dense freckles get darker early on.  She may also have given spot treatment to the more dense ones today to see what would happen to the less dense ones.  It will work after a proper series of treatments, usually 4-5. Hope this helps.