I think it's a trial step for PayPal and they may continue to develop further with broader features and functionality like full crypto-exchange if they see a good opportunity.
Since PayPal just announced that crypto trading and payment services went live in the US, do you think PayPal may turn into a big competitor to existing cryptoexchages? They can also launch a crypto-currency trading desk as well, why not.
As you can see, they didn't open an exchange immediately but are using another exchange as a medium to buy BTC for their customers who put their money in crypto through PayPal (at least that is what they wrote in it). Now, it's impossible for PayPal to match the total number of BTC's demand for their wide range of users which is why they are not allowing us to withdraw our crypto but just keep it inside, see it and sell it when we see the value increased. Do you really think they are looking into any such business like entering an exchange business, that too crypto? I don't think so.