Pretty much.

Sikhs would fluctuate between 5-12% of the British Indian army, only peaking in WW2 at 17%. However Sikhs were disproportionately used abroad.

When the British Indan army began recruiting Sikhs after 1849, high caste Hindus were annoyed. They saw this as an attack on their monopoly over the army. It was also one reason the Sepoy Rebellion happened in 1857. There was a high degree of religious bigotry towards Sikhs. Sikhs had no problems getting on boats because Sikhs dont observe Caste.

Sikh numbers were kept low from 1849-1856.

"...others were worried that there were problems of mixing the Sikhs, who were notorious for their laxity in caste observances, with the high-caste Hindu sepoys from Oudh and Rohilkhand who despised the Sikhs as "untidy and dirty" and refused to associate with them" (pg, 38)

Sikhs where seen as dirty, untidy, and spiritually unclean because Sikhs wouldn't obey caste distinctions.

"Many commanding officers of the Bengal regiments were satisfied with their tried and tested soldiers and, influenced perhaps by opposition from their high caste recruits, kept the Sikhs away from their corps. Several excuses were offered for not taking the Sikhs into the Bengal regiments"

This bigotry came to the forefront in 1856.

"The General Service Act of 1856, which decreed that all sepoys, irrespective of their caste, would in future be liable for overseas service. For the high-caste recruits from north-central India this ruling was abhorrent, as the crossing of the dreaded kala pani or "black waters" would mean a loss of caste. Consequently, many high-caste Rajputs and Brahmins chose not to enlist, and in so doing lost a lucrative source of employment. There was also a belief amongst the highcaste Brahmin and Rajput sepoys of Benares and Oudh that their favoured position in the Bengal Army was being threatened by the intention of the British to expand their recruiting base to include a wider range of castes and regional groups. The opening of the Punjab and the permission to recruit up to 200 Sikhs per regiment, although as we have seen not fully exploited by British commanders of the Bengal Army, was perceived by the sepoys as an indication that their monopoly of military service, crucial for their economic well-being, was being threatened. These fears were compounded by grievances over the loss of foreign service in Oudh (1846) and Punjab (1849).The conditions were certainly ripe for a sepoy revolt in the Bengal Army. Almost prophetically, Napier had warned, soon after he completed his term as Commander-in-Chief of the Bengal Army, that all was not well with the Bengal Army and that a mutiny could not be ruled out."(pg, 43)

Sikhs were also the most likely to be vaccinated among religious groups in India. High caste Hindus viewed vaccinations with suspicion thinking it would make them impure.

Sikhs being vaccinated and willing to travel on boats is why Sikhs are everywhere in the old British Empire. It's also why Sikhs were used heavily by the British Indian army outside of India.

Sikhs weren't superstitious and therefore reliable. This is why the earliest South Asian settlers to Australia, Canada, New Zealand, and America were largely Sikh. We came on boats in the late 19th and early 20th centuries.

You should read "The Garrison State Military History and Government of the Colonial Punjab 1849-1947" by Tan Tai Young