There's a couple of reasons: 1) In an investment bank such as...

There's a couple of reasons:

1) In an investment bank such as GS, equities research is totally independent of the other parts. There are strict "Chinese Walls" that prevent sharing of information and co-ordinated decision making. As an example, a GS private wealth advisor has every right to direct client funds into a stock even if equities research has it as a sell. Another example would be that GS could be advising a bidder for a company and may acquire stock on behalf of the bidder so that the bidder remains anonymous. There are many other such services that could lead to this situation. The point is that they are independent of equities research.

2) Banks such as GS hold shares on behalf of others as the Nominee - it's highly unlikely that GS itself has taken a position in the stock. They are an institutional broker after all who buy and sell shares for clients on the client's direction. The rules around substantial shareholder disclosures mean that all the holdings where GS is the nominee get aggregated under their name, but the beneficial owner of the shares can be totally unaffiliated with GS.

This stuff is very common - look at any ASX 100 company and you may see NAB, CBA, MQG, ANZ etc as substantial shareholders - when you dig into it you see that NAB is holding on behalf of subsidiaries (e.g. MLC Wealth Management who is holding shares for 1000s of its clients). Same deal goes for GS