I am afraid, your observations and conclusions are incorrect.

Wong, Lee (pronounced as Lei), Loo (pronounced and spelled as Law nowadays) are the Cantonese readings of Chinese names; whereas Wang, Li and Lü are Mandarin pronounciations of 王, 李 and 魯, respectively.

Lee (as «e» in Padme from the Star Wars) and Loo («oo» as in «door») are an artefact of one of the first attempts by the British to come up with the standardised English spelling for Chinese names they had perceived through the lens of the Cantonese language and culture. One would have to look back into the history of Europeans coming into the first contact with the Chinese civilisation, of which the British had been one of the first frontiers (let's not digress into a discussion of the historical background nor merits of that having taken place, for that is not the point I am trying to bring across).

The British had come into their first contact with the Qing China through Canton in the late 18th century where Cantonese was the prevailing language, with Mandarin (官話) being relegated to the status of the language of mandarins, the Chinese imperial court and those willing to pass imperial exams. It took the British (and European missionaries) a few decades to realise that China had had a multitude of different – often mutually unintelligible – Chinese languages, in which the same character (漢字) had a distinct pronunciation. Speakers of their own mother tongue (be it a Yue, Wu, Gan etc language) would pronounce the same 漢字 according to phonetic rules of their own native tongue. For instance, 林 is pronounced as «Lam» in Cantonese but as «Lin» in Mandarin; 吳 is «Ng» in Cantonese, but it is pronounced as «Goh» in Teochew and as «Wu» in Mandarin; likewise, 金 is «Gan» (Cantonese) vs «Jian» (Mandarin), 等等...

The first migration wave out of China into the US mostly came from Lingnan (the area encompassing Gwong Sai, Gwong Dung, Hoi Naam and parts of the today's northern Vietnam). The majority of them, however, spoke Teochew – a Yue Chinese language, that is related but is not mutually intelligible with Cantonese. US Chinatown dwellers used to speak Teochew for over a century before Cantonese started to take hold in the second half of the 20th century.

Since the migration of Chinese nationals had been forbidden since the times of the Ming dynasty, and with the British controlling the Canton port in the late 19th century onwards, Canton (Gwong Jau nowadays) was pretty much the only viable exit point for migrants out of China seeking an escape from the Qing for their own reasons; hence they would have had to obtain the exit immigration documents at Canton with their Teochew names spelled out using the English spelling the British had adopted for spelling out the Cantonese names earlier on. Hence Wong, Lee and Loo and not Wang, Li or Lü (or actual Teochew spelling). The former ones are in active use in Hong Kong today, whereas the latter ones are encountered in the mainland Chinese names.