Search result anomaly in GitHub Search API for Repositories

We have a requirement to search repositories by their name within a given organization. For this we are using GitHub search API.

I have following test data in my GitHub enterprise server,

Organization : testOrg2
Repositories within testOrg2 are as follows,

  • testRepo4
  • testRepo5
  • testRepo6

I am suing following endpoint for searching…
/api/v3/search/repositories

When I am searching with following search keywords, I am getting the expected results,

test
repo
testRepo
6

But, If i search with some middle sub-strings such as follows, I am not getting any matched results,

est
epo
estRepo

Sample search query for above cases is as follows,
https://10.66.60.202/api/v3/search/repositories?per_page=100&q=%22Repo%22in:name+org:%22testorg2%22&page=1&

I want to know whether this is a limitation in GitHub API or whether we are doing something wrong.