You should definitely be surprised. Just because he was seen as a near-lock to sign, doesn't mean that his negotiation tactic would be to accept the first deal thrown at him. Maese had multiple potential suitors in the supplemental first to 2nd rounds, Chris Crawford even mentioned that he had heard that we were considering him with our FIRST pick. The other big "pop-up" HS pitcher was Anthony Guardado who was drafted two picks before Maese, and he ended up signing for $550K or just barely under slot at his pick. So you're Justin Maese and you're hearing your name now solidly associated as a ~top 3 round talent, you've hit 96mph, and you've got a pretty decent Texas Tech scholly. You get drafted in the 3rd round (again, the range within which you expected) and you almost immediately sign for what is essentially the slot value of the first pick of the 6th round? It doesn't add up from a logical sense at all.
The Jays only have those excess funds if they go right up to their taxable limit, which is far from a certainty. Look at the news about Marrick Crouse turning down $500K, and then Pruitt signing right after for that same amount. Why would they turn down Crouse over a measly $100K if they were still operating under the impression that they have $400K+ left? If anything, it makes it look very much as if it came down to Pruitt/Crouse getting that one big $500K offer, with it being a "first one to take the offer gets it" approach. I think that Maese's deal is definitely relevant because if you look at the overall flow of money, the savings almost perfectly line up with the $500K excess that was spent on Pruitt and Christian Williams, with some wiggle room in there to throw a bit more at Singer if its required or maybe another ~$100K overslot type deal (ala C. Williams).
I don't think those scenarios match up at all. Alford was drafted in the 3rd round; as a kid who had told everyone not to draft him and that he wasn't signing, that high of a selection was a pretty strong indicator that the Jays knew they could get him signed (although it ended up taking a super-generous offer for Alford). Brentz and Tellez were similar cases as Pruitt (late round flier picks), but in those two scenarios we knew well ahead of time that we'd probably land at least one if not realistically both for the sheer fact that we knew well ahead of the deadline that Bickford wasn't going to sign. In this scenario, I'm confident that Maese's savings made this Pruitt signing an actual possibility, and no matter what you try and argue, Maese signing for only $300K (less than HALF his pick value) was a very shocking move. Like I said, don't be surprised if we find out that Maese has a partial tear in his elbow or something down the line, with that being the reason why he was so willing to take so little money.