Software is considered "open source"1 as long as it satisfies at least one of the widely-accepted definitions, like OSD, FSD, DFSG etc. It's possible for a piece of software to both spy on its users / violate their privacy and still be open source; the two properties are orthogonal.
However, you may find that among the open source communities, a disproportionate amount are concerned with privacy, and consider telemetrics as spyware and unethical. The FSF is a notable example of this; one of their raisons d'etre is that proprietary software violates users' freedoms, such as privacy through spyware. The argument goes, even if such spying exists in open source software, it can be easily removed by the user.
You asked whether "it's OK" to have telemetry in open source. It's clearly legal, as there's nothing stopping you from using an open source license on whatever software2. The answer will depend on who you ask:
- Whether the telemetry in question are ok (e.g. some people consider opt-in, anonymised telemetry ethical)
- Whether any telemetry is ok (some consider all telemetry unethical)
- Whether being open source is all that matters (i.e. caveat emptor; if you don't like it then change the source)
1: free software, libre, etc.
2: as far as copyright law is concerned. There may be other laws governing the legality of software, such as patent law, or restrictions on encryption and national security.