I take "stifling the development of search engines" to mean Google using its position to prevent someone from engaging in the software development of code, trying to sell any alternative to its offering, preventing market entry at all.

I just think it's a whole other level of argument to say that someone not having access to the same data and only being able to develop an inferior search technology = anticompetitive. (where the "not having as good data" part is not done by denying other competitors access to some resource that they should have a right to, or could equally gather on their own)