Yes dwell angle is  still a factor in  transistorized ignitions.  It is no
longer adjustable but through software it is possible in distributorless
ignitions,   but  no the service tech cannot do so.
 Dwell is  expressed in  degrees of distributor shaft rotation.   30*dwell
on an eight cylinder engine  would leave  120*  of  cumulative rotation for
the coil to  be off charge and therefore cooling somewhat. 45* on a four
cylinder engine would  leave 180* to cool,  and 180* to charge the coil
cumulatively. Simply because the distributor shaft rotates 360* of course.
If you have a transistorized ignition, breakerless whatever, you  can still
measure the dwell angle.  If the system is weak  chances are you will find a
shorter dwell angle when you test it.  I have done this and I know it works.
In fact,  transistorized ignitions can and do have variable dwell periods
factored  into the circuitry  on some  applications. In reality the hall
effect sensor is simply a switch and not the conductor that all current must
pass  to charge the coil and this  leaves  you many possibilities.
  To understand this best it is best to realize that dwell exists even in
distributorless ignitions, though it is   often ignored, it is  a percentage
of  time in a given engine revolution.  That doesn't matter but that it is
important to realize that   without contact points you do still have a dwell
angle.

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