It's absolutely not the case. It's more like a conspiracy theory that keeps getting pushed into Bitcoin-related threads at Hacker news (maybe to tilt future analysis?)
If we take a look at the past month of commits from https://github.com/bitcoin/bitcoin/pulse/monthly, the top ten authors are:
- MarcoFalke
- fanquake
- hebasto
- ajtowns
- glozow
- ismaelsaadeq
- TheCharlatan
- instagibbs
- brunoerg
- mzumsande
None of them works at Blockstream.
When you say "long ago", it likely points to the "Bitcoin Cash" incident. Almost every person that knows of Bitcoin Cash thinks that Bitcoin is a scam; almost everyone else laughs at the idea of Bitcoin Cash working.
Long ago, that was also the case: https://old.reddit.com/r/Bitcoin/comments/61blfg/blockstream...
(edited for format)