I wouldn't say that at all.
I've met a couple of Sikhs here in Canada and anyone here can attest to the fact that when you ask them what they are they'll refer to themselves outright as Punjabi not "Indian".
I've yet to meet a single Sikh that didn't call themselves Punjabi rather than Indian.
The three I've known best, two are bros and another one who is actually an acquaintance of a cousin of mine, absolutely hate India. They definitely can't speak for the entire Sikh community but of the three I know personally the fact that 100% of them hate India was pretty eye opening.
In fact there was a documentary on the CBC about the anti-India rhetoric within the Sikh community here in Canada. It's so bad that even Manmohar Singh, former Indian PM and a Sikh himself, was forced to deal with this issue when he met Canadian PM Harper back in 2012.
thestar.com/news/canada/2012/11/05/indian_politicians_express_concern_to_stephen_harper_about_sikh_extremism.html
If you ever come across their festivals, though you can probably see some video online, it's pretty evident.
Now that said it doesn't mean that they're "pro Pakistan" in the way you might be thinking.
When violence broke out in 1947 who do you think was involved in the murdering of Muslims trying to make their way to the Islamic Republic of Pakistan? Yeah, the Sikhs.
They're basically okay with anyone that hates India and Hindus. However, that doesn't mean they like Muslims and Pakistan (Muslims and Sikhs have regularly fought in the UK) they just don't have an interest in going to war with us anymore and not sure how many within their ranks support this but there are definitely some who would be happier joining Pakistan if only to save Punjab and their community in Kashmir from Hindu India.
At least with regards to an independent Khalistan Pakistani's should be cooperating with their community. We can participate in each others protests against India and it adds increased legitimacy to each of our struggles which, if you think about it, are actually intertwined since an independent Khalistan also assures an end to the occupation of Kashmir (India would need to cross Khalistan to enter into Kashmir which they wouldn't be able to do).
However you can be sure democratic secular India would be more than happy to slaughter every Sikh in occupied Khalistan but Islamic Republic Pakistan would be more than happy to come to their defence.
Personally I believe in the absolute right of the Sikhs to carve out an independent Khalistan.
Woodrow Wilson said it best:
"India is a geographical term. It is no more a united nation than the Equator."
Pakistan should be working with these individuals not just in India but abroad just as we should be working with China to support those who want an independent Assam, etc... No one should be forced to live under their occupation.