@opheliadesign the many function calls is probably inherent in OOP design with all of the dependencies. You are continually calling parents of parents of parents.
I wouldn't worry that it didn't happen in L4.2 - for all you know, it may have got to 99 recursive function calls itself and just didn't trigger the XDebug limit.
Since XDebug themselves have realised the limit is too low and changed it, it appears that it's just the way things are headed.
Also it's not just Laravel that has this "problem", it's widespread. Take a look at this Symfony issue:
https://github.com/symfony/symfony/issues/13998
Well, looks like the dependency graph is deep enough to reach the limit of 100.
100 nested calls is pretty easy to reach when dealing with recursive structures
and...
Setting xdebug.max_nesting_level = 112 works with the 2.6.5 version (111 fails). With the previous 2.6.4 I can get away with max_nesting_level = 91 (90 fails). So the new version increases the nesting by 21 levels for this particular case, or about 20%.
So it looks like it's the changes in Symfony that have caused the increase.
Of course you could have researched this yourself if it really bothered you that much ;-P