Slowdown in writing code (to changes?) in 7 vs 6

Writing code in this way seems to be about 2.4 times slower in Pharo 7
vs Pharo 6.
I also tried with smaller numbers, and there I noticed a rather high
number of calls
to File>>basicOpenForWrite:. With 4*4*4 methods, 768, and 5*5*5 1502.

|organizer aToZ|

organizer := RPackageOrganizer default.

aToZ := 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

[ aToZ do: [ :ch | |packageName package|
     packageName := 'Package', ch asString.
     package := organizer createPackageNamed: packageName.
     aToZ do: [ :classCh | |cls|
         cls := Object subclass: (ch asString, 'Class', classCh asString)
asSymbol
             instanceVariableNames: ''
             classVariableNames: ''
             poolDictionaries: ''
             package: packageName.
          package addClassDefinition: cls.
          aToZ do: [ :m |
              cls compile: m asString asLowercase, String cr, ' ^self' ]
] ] ] timeProfile

(221 s vs 93)

Do I need all those calls to #basicOpenForWrite?

Stephan