Leaked documents obtained by Motherboard indicate that recent changes to Apple's policies regarding repairs may make it almost impossible for you to repair your malfunctioning 2018 MacBook Pro or iMac Pro without going to an Apple Store or an Apple Authorized Service Provider.
The change seems to be related to the T2 security chip, which the Cupertino giant started adding to its newer machines starting with the iMac Pro last year. Any repairs to the display, logic board, Touch ID, keyboard, battery, trackpad, or speakers of a MacBook Pro and the logic board or flash storage of an iMac Pro will now require the use of proprietary software diagnostics software.
This software, called Apple Service Toolkit 2, is only provided by Apple to its Authorized Service Providers, and without it, any repairs to the aforementioned parts will result in "an inoperative system and an incomplete repair". This essentially bars third-party repairs, and would also make it difficult to fix said machines once they are classified as vintage machines.
The changes are exclusive to Macs which include the T2 chip, and it's unclear at this moment if the change is an irreversible requirement due to the security features of the chip. The other possibility, as pointed out by iFixit's CEO in a statement to Motherboard, could be that Apple is looking to more finely control how its devices are repaired, thus increasing the chances of users upgrading to newer models early.